1 QUESTION BANK FOR JUNIOR ENGINEER (ELECTRICAL / GENERAL SERVICES) SELECTION TEST - PREPARED BY ESTC/LGD
2 QUESTION BANK FOR AIR-CONDITIONED COACHES
Write short notes:
2 QUESTION BANK FOR AIR-CONDITIONED COACHES
Write short notes:
1. Define Refrigeration? Refrigeration is the process of lowering the temperature of a body below that of its surroundings.
2. Define Air-Conditioning? The process of treating the air so as to control simultaneously its temperature, humidity, cleanliness and distribution to meet the requirements of the conditioned space.
3. What is the unit of refrigeration/Air conditioning? The unit of refrigeration / Air-conditioning is Ton of refrigeration.
4. What is one ton of refrigeration?
One ton of refrigeration is latent heat required to melt a ton of ice at 32 degrees F in 24 hours. One short ton = 2000 lbs. Latent heat of fusion is 144 BTU/lb OR A ton of refrigeration is the rate of heat removal equal to;
In FPS system 1 ton of refrigeration = 2000 x144 = 2,88,000
B.T. U/24 hours = 12,000
B.T. U/hour = 200 B.T.U /min.
The rate of cooling has been designated as a ton of refrigeration. It is measurement of the rate of transfer.
In MKS system One ton of refrigeration = 72000 k cal/24
hours = 3000 k cal / hour
= 50 k cal/min
One ton of refrigeration is latent heat required to melt a ton of ice at 32 degrees F in 24 hours. One short ton = 2000 lbs. Latent heat of fusion is 144 BTU/lb OR A ton of refrigeration is the rate of heat removal equal to;
In FPS system 1 ton of refrigeration = 2000 x144 = 2,88,000
B.T. U/24 hours = 12,000
B.T. U/hour = 200 B.T.U /min.
The rate of cooling has been designated as a ton of refrigeration. It is measurement of the rate of transfer.
In MKS system One ton of refrigeration = 72000 k cal/24
hours = 3000 k cal / hour
= 50 k cal/min
5. Discuss various operations of vapor compression Air condition cycle?
A. Vapour compression system of air conditioning In the refrigeration cycle, Freon – 12 or Freon -22 is used as refrigerant and the system is so designed that it changes the state of refrigerant at various 4 stages.
1. Compression
2. Condensation
3. Expansion
4. Evaporation
Compression : Refrigerant is drawn from evaporator in dry vapour state by suction strokes of the compressor. In compression stroke, the refrigerant temperature and pressure being increases to the condensation cooling level.
Compression : Refrigerant is drawn from evaporator in dry vapour state by suction strokes of the compressor. In compression stroke, the refrigerant temperature and pressure being increases to the condensation cooling level.
Condensation: High temperature refrigerant is received in condenser unit where the heat is rejected with the help of water and natural air of condenser fan, which results refrigerant returns to liquid state.
Expansion : After condensation, refrigerant is stored in receiver in – liquid state till it needed by expansion valve. Expansion valve is provided just before evaporator unit; the refrigerant passes through this valve and enters this evaporator unit with low temperature. Evaporation: Expanded/spreaded low pressure refrigerant enters into the evaporator unit or refrigerated space and converted in to vapour form and thus refrigeration cycle is completed. At this stage refrigerant observes the heat through circulating air with the help of blower fan.
6. Explain the Refrigeration system with a neat diagram.
The refrigeration system consists of 4 basic major components and refrigerant. Compressor, Condenser, Expansion device and evaporator. The refrigerant system depends for its action on latent heat principle and expansion principle.
The refrigerant in gas form is sucked into the suction side of the compressor and compressed to high pressure. From the compressor, the gas goes through a condenser which removes the sensible heat generate in the gas due to compression as well as, the latent heat and the gas liquefies. The liquid gas passing through an expansion valve into the evaporator is expanded to gas absorbing the latent heat in the process, thus cooling the cooling coil. The gas having taken up its latent heat in properly designed cooling coil is now dry and is again sucked into the compressor to continue on another cycle.
2.1 Refrigerants are heat carrying medium which during their cycle in the refrigerant system absorb heat at a low temperature level and discard the heat so absorbed at a higher level. The refrigerants common used are R-12, R-22, R-134a etc. The refrigerant have boiling points much below ordinary room temperature, so they exists as gas and are only held in the liquid state by keeping them under pressure. Refrigeration can be produced by allowing a liquid refrigerant from high pressure vessel to pass and boil inside a coil or evaporator. The latent heat needed for the boiling is taken from the surrounding space of the evaporator, thereby cooling the space. After passing from evaporator, the refrigerant is reclaimed with the help of compressor. The compressor compressed the vapour to the pressure corresponding to a saturation temperature, higher than the temperature of naturally available air or water. The compressor also circulates the refrigerant through the system. The refrigeration cycle thus comprise of:
7. List out Refrigeration tools? Flaring tool, crimping tool, tube bender, pinching tool, swedging tool, for pipe, charging line, pipe wrench, adjustable spanner and spanner set.
8. List out types of AC Coaches?
a) Under slung Conventional AC Coaches and roof mounted package unit fitted AC Coaches. AC First class, AC II tier, AC III tier, AC Composite, AC Chair cars.
9. List out parts of Under Slung AC coach? Compressor, Compressor motor, condenser, condenser fan motors, liquid receiver, dehydrator cum filter, thermostatic expansion valve, evaporator, blower motor, fresh air filter, return air filter, 18 KW Alternator, Rectifier cum regulating unit, 800 AH battery, pre-cooling transformerrectifier unit.
10. What are the parts of electronic thermostat used in RMPU AC coaches?
A) The electronic controller
B) Remote sensor
11. What are temperature setting recommended by RDSO in case of electronic thermostat?
As per the RDSO recommendations the temperature in the coach should be with electronic thermostat
Plant cut in temperature in summer - 25°C
Plant cut out temperature in summer - 23°C
Plant cut in temperature in winter - 19°C
Plant cut out temperature in summer - 21°C 5
12. Explain about Electronic thermostat used in AC coaches?
The unit is intended to provide ON/OFF control of the refrigeration plant/heater by sensing the temperature of the air at the return air grill.
The unit except the sensor shall be mounted in AC control panel, which is in the non-air conditioned space, and the sensor shall be mounted at the return air grill of the air conditioned space. The unit shall be designed for continuous operation. The unit shall give output signals through the contacts of the relays at the final stage of it to switch on either the heating control circuit or the cooling (refrigeration plant) control circuit. The operating point of the relay corresponds to the heater shall be capable of being selected between 17 & 21 deg. C. The operating point of the relay corresponds to the refrigeration plant shall be capable of being selected between 22 & 26 deg. C. The desired settings for the heating and cooling shall be obtainable in the following steps. The temperature setting are given in deg. C
Cooling Heating
Medium - 25 19
High - 23 21
The drift on the selected settings (due to variation in ambient temperature, input voltage fluctuations, ageing of the components and error on account of any other reason) shall not be more than +/- 0.2 deg. C. The differential between the cut-in and cut-out operation of the Heater/Refrigeration plant shall be between 0.5 deg. C minimum and 1.0 deg. C maximum.
At final stage of the unit there shall be two relays one for the heating control circuit to switch on the heater through its contactor and the other for the cooling circuit to switch on the refrigeration plant through its contractor. Each relay shall have one N/O and one N/C contact. The relay used for heater circuit shall get energized when the temperature at the sensor is less than the set value for heating and the relay that used for refrigeration plant shall get energize when the temperature at the sensor is more than the set value for cooling. The contacts of these relays shall be rated for and inductive load of 3 amp at 110V ac PWM power supply.
The unit shall be capable to work from 110V ac +/- 10% PWM supply with maximum ripple content of 15%. The design shall take care of the series connections and the surges that may be present due to switching ON/OFF of these loads controller shall be design in such a manner so that relay operation is chattering free.
The unit shall be provided with reverse polarity protection against inadvertent wrong connections of the polarity of the power supply.
The unit shall be designed to take care of an over voltage of 200V for one minute at the power supply terminals.
13. List out parts of RMPU AC coach? Hermetically sealed compressor, condenser, condenser fan motor, capillary tube, Accumulator, Evaporator, Blower motor, Fresh air and Return air filters, 25 KW Alternator, Rectifier- Regulator units, 1100 AH battery, pre-cooling rectifier units, 25 KVA inverters.
14. Compare between RMPU and Under slung AC unit? Comparison of Roof Mounted Ac,
15. List out types of WRA? WRA with DC Motor and compressor WRA with AC Motor and compressor 3-phase self priming mono block pumps.
16. How many types of gauges used in AC coach? Pressure gauge, compound gauge, LP gauge, HP gauge, and oil pressure gauge.
17. What are the operating Pressures of Under Slung AC coaches? LP = 37 to 46 psi HP = 150 to 180 psi OP = 70 to 90 psi
18. Draw the tube light circuit diagram?
19. What is the function of AC compressor? Compressor: It has two fold functions. It removes Vapor from the evaporator at a rate, which will permit steady state conditions of temperature and pressure in the evaporator. It discharges the Vapour at a pressure and temperature high enough to permit heat rejection along a descending temperature gradient to the cooling water or air of the condenser
20. Rating of the fuse used for phase supply & field supply in Regulator of AC Coaches. Phase supply fuse for 25KW Regulator – 160 Amperes. Field supply fuse for 25KW Regulator – 6 Amperes.
21. What is the capacity of cells used in AC Coaches? 800AH in under slung conventional AC coaches and 1100AH in RMPU AC coaches.
22. Action to be taken if Compressor Short Cycles.
23. Action to be taken if compressor runs continuously.
12.1.3 Compressor Runs Continuously
High discharge
a) Discharge shut off valves not fully opened.
b) Air or non condensable gas in the system.
c) The condenser pipes are blocked by mud or scales.
d) Too much refrigerant in the system. Open valve. Purge the foul gas from the condenser. Clean the condenser pipes. Drain off the refrigerant into the empty cylinder.
24. Reason for low suction pressure. Sr. No Trouble Possible Causes Suggested remedies 1 Low suction pressure
25. Give reason for less cooling and remedies. Inadequate Cooling
26. Describe procedure for replacement of Maneurope Compressor. Procedure for replacement of Compressor:
Leak Test:
Disconnect the low pressure cut-out and pressure-charge the system with dry nitrogen at 24 kg/cm2 (350 psig) and check for leakage with soap solution.
Evacuation :
After leak test, connect the system on both the low & high side to a vacuum pump for at least 4 hours and pull up to 200 microns (29.9 inch Mercury Column) of vacuum. Use electronic or tube type gauge, for checking vacuum.
Charging:
Now charge the system with 2.85 kg R-22 gas. This can be done by pulling a vacuum on a 5 kg gas cylinder and charging it with 2.85 kg R-22 gas by weight. (Weight the cylinder before and after filling gas. The difference should be 2.85 kg in weight). Check with halogen leak detector after charging the system.
28. What is the normal current drawn by RMPU AC plant?
Normal currents for various equipment are as under:
Package in cooling : 10 - 21 Amps (SIDWAL) mode 18 - 20 Amps.(Feeders)
Compressor motor : 7.5 to 9.0 Amps.
Condenser motor : 1- 1.5 Amp (Feeders)
each 1.8- 2.3 Amp(SIDWAL) each Blower motor : 2.0 - 2.3 Amp.
Each Heaters : 8 Amps. each.
29. AC Plant not working in auto mode.
What action you are going to take. Check for the proper working of PCB and Thermostats.
Keep the package in the auto mode. Run the blower. Short points 3 and 4 PCB. The compressor should come 'ON'.
Open the points 5 and 6 heater should come on. Operate the machine manually in case of thermostat failure or PCB failure.
Shift Rotary - Switch RSW-4 from "AUTO' to "COOL-ING or I-EATING manual mode.
The AC Unit will now operate continuously thus by-passing the Thermostat. During manual operation thermostat goes out of the control circuit and machine will run continuously in the selected mode of operation.
In case of excessive cooling, the compressor will switch off from low pressure cut-out and in case of excessive heating, the heater will switch off from the safety thermostat. The ACCI should switch ON /OFF the plants by monitoring the temperature inside the coach with a thermometer.
30. What is Cut in & Cut of pressure of WRA Cut out
CUT IN --- 0.3 Kg/sq.cm
CUT OUT -- 0.7 Kg/sq.cm
31. What are major differences in equipment and operation of Air conditioning system under slung and RMPU equipped coaches.
32. What are the AC system presently being used in our Railways and mention the feature of each type and where they are used. Two types of AC system are being used Viz., RMPU fitted AC Coaches and Under slung conventional AC Coaches. Both these coaches employed Vapour compression system for refrigeration. RMPU:
1) This is hermitically sealed system with no fittings or openings and used 3-phase AC Motors. Hence less maintenance
2) Uses Refrifirent R-22 apply 3 kgs.
3) The package is mounted on the roof thus dirt or dust collection in condensers negligible, No chance of damage due to the flash floods, cattle run or flying ballast.
UNDERSLUNG: The compressor used is open type which can be easily be attended in case of repairs. The compressor moor and compressor are both separate units. Defective motor will not have any effect on the compressor. The system is easy to understand because of provision of pressure gauges. The refrigerant used is R12 approximately 15 kgs.
33. What are the refrigerants generally used in Air conditioning system. What are the required properties of refrigerant?
Refrigerant – 12 and 22 are used in under slung conventional AC Coaches. And RMPU AC Coaches respectively.
13 Recently Railways has introduced use of R-134 A environment friendly refrigerant and some of the RMPU coaches have been converted into R-134 A refrigerant.
REQUIRED PROPERTIES:
1) The refrigerant shall be non poisonous, non inflammable, non corrosive and non irritating.
2) It shall have no harmful effect on the taste, colour or Aroma of food and drinking water.
3) It shall have low boiling point
4) It shall have high latent heat of vaporization
5) It shall have low volume per kg. When in gaseous state
6) It shall have high coefficient of performance
7) Easy detection of refrigerant leakage
8) It shall be cheap and readily available in the market.
34. What are the essentialities of coach Air conditioning?
The essentialities are -- The working of blower fan of the evaporator and the blower fan of the condenser has to be ensured before the compressor starts functioning
-- Suitable protection to ensure proper lubrication of the compressor to avoid piston seizure.
-- The excessive pressure on the discharge side of the compressor should be avoided
-- The suction pressure should not be lower than specified to prevent frosting of the evaporator and liquid entry into the compressor
-- All the motors should not be switched at a time to prevent sudden inrush of starting current.
-- A suitable interlock has to be provided to ensure that heater is not on, when compressor is working.
-- Low voltage protection is required in order to avoid undue drain on battery
-- The blower fan has to come ON before the heater compressor ON.
-- Over load protection and short circuit protection for all electrical circuits.
35. What are the different types of AC coaches presently in use, explain theca system in coach in brief. Two types of AC system are being used Viz., RMPU fitted AC Coaches and Under slung conventional AC Coaches. Both these coaches employed Vapour compression system for refrigeration.
RMPU:
1) This is hermitically sealed system with no fittings or openings and used 3-phase AC Motors. Hence less maintenance
2) Uses Refrigerant R-22 apply 3 kgs.
3) The package is mounted on the roof thus dirt or dust collection in condensers negligible, No chance of damage due to the flash floods, cattle run or flying ballast. UNDERSLUNG: The compressor used is open type which can be easily be attended in case of repairs. The compressor moor and compressor are both separate units. Defective motor 14 will not have any effect on the compressor. The system is easy to understand because of provision of pressure gauges.
The refrigerant used is R12 approximately 15 kgs. Also
1. Self generating AC coaches: - In these AC coaches each coach is equipped with its own generating equipment like 3-phase Alternator and a set of battery to cater to the requirement of total electrical load of the coach. It is also equipped with a Pre-cooling transformerRectifier unit for taking shore supply.
2. End on generation AC coaches: - In trains like Rajdhani express & Shatabdi express the coaches depend on the power supply from Power cars. The rake of the train is provided with a power car having two nos of Diesel generators, one will be working and the other is standby. This power car is placed at the end of the rake formation. The supply is fed to all the AC coaches with the help of inter vehicle couplers. 36. Write short notes on the following:
a) Refrigerator Refrigerators operates on the Vapour compression system having hermitically sealed compressor mounted at the base of the cabinet. Refrigerant used is R-22 or 134
A. Expansion valve used is capillary tube. The evaporator piping is fastened round and brazed to the freezer box. The condenser tube is placed over a single metal sheet for dissipation of heat. The top space is freezer unit. and the rest of the cabinet interior gets cooled by convection currents of air set up by freezer unit.
b) Water cooler: - Water cooler is a machine working on refrigeration system for cooling water for drinking purpose. The refrigeration system is same which is utilized in airconditioning, refrigerators, etc. Generally two types of water coolers are used i.e., Instantaneous water coolers and storage type water coolers. In addition to the above two types there are also storage-cum-instantaneous type also. The drinking water having temperature between 10 degree C to 13 degree C is preferred.
c) Window type AC units: - These are completely self contained units, with the compressor, condenser, evaporator, refrigerant piping and air filter, all assembled in a very compact assembly. The window units are usually of ½ to 2 tons capacity and fitted with 230 volts motor. The refrigerant is controlled with the capillary system. The unit is so designed that it can be mounted on the window with small bracket from outside.
d) Air filter in ac system: Air filters are used to maintain cleanliness / dustproof. There are mainly two types of air filters. Viz., Return air filter is to remove any dust present in AC room/Coach and fresh air filter is used to filter fresh air for dust etc.,
e) Evaporator in refrigerator system: This constitutes the cooling unit, in which the liquid refrigerant under low pressure evaporates and in doing so, it takes away its quota of latent heat, there by cooling the medium surrounding the cooling coil.
f) Dry and Wet bulb temperature: Dry bulb temperature is the temperature of air as measured by an ordinary thermometer. 15 Wet bulb temperature is the temperature of air as measured by an ordinary thermometer, whose glass bulb is covered by a thin cotton sleeve soaked in water.
g) Condenser: It is intended for cooling the hot gas and liquefying it under pressure. It may be air cooled or water cooled
h) Sealed compressor of AC unit: The motor and the compressor unit is housed in one casing and completely sealed. The suction and discharge piping is brazed as no valves are used , the chances of leakage is eliminated.
37. What is difference between dry bulb and Wet bulb? Dry bulb is the temperature of air as measured by an ordinary thermometer whereas wet bulb temperature is the temperature measured by an ordinary thermometer, whose glass bulb is covered by a thin cotton sleeve soaked in water.
38. What is difference between humidity and relative humidity?
Humidity is the amount of water vapour present in the air whereas Relative Humidity is the ratio of the actual amount of water vapour contained to the maximum amount required for saturation and is expressed as a percentage.
39. What is meant by due point?
It is the temperature of air at which the moisture present in air starts condensing.
40. What will happen if the AC plant capacity is insufficient for load?
If the AC plant is insufficient for the load the desired temperature will not be attained in the room. The AC plant will run continuously under vapor pressure rises considerably overloading the compressor. The condensation of the refrigir3nt will not takes place in the condenser.
41. How is any leak of the refrigerant detected in refrigerating circuit. When the LP and HP pressures are persistently low and cooling is insufficient, frosting of evaporator, it shows less gas in the system giving indication that there is leakage of refrigerant from the system. Leakages can be detected by conducting low pressure test on suction side and high pressure test on discharge side of the system.
42. How do you attend to a leak joint?
Soap water is applied on the piping and equipments. If any leakage is there, bubbles will form on the soap fomentation. That place is to be brazed / repaired.
43. What is the procedure for final testing and commissioning of a new AC plant Package system?
As per the RDSO code of practice RDSO/PE/O/0008-2005 REV.O the following are the measures to be adopted for prevention of fires on AC coaches:
i. The air-conditioned coaches are to be provided with elastomeric copper cables if the size is more than 10 sq.mm. in case of old coaches.
ii. The air-conditioned coaches are to be provided with PVC cooper cables if the size is less than 10 sq.mm. in case of old coaches
iii. For new AC coaches E-Beam irradiated thin walled elastomeric cables are to be used. iv. The number of joints and junction boxes should be minimum.
v. Correct size of cables is to be provided for different circuits as per load.
vi. All the cables other than branch cables shall be secured to the coach structure by cleats located at an interval not exceeding 500 mm.
vii. All the cables other than branch cables either side of bend and near all end connections, extra cleats are to be provided not exceed a distance of 150 mm.
viii. The edges of the groove for holding the cables in the two halves of the cleat shall be suitably chamfered to avoid pinching of cable insulation.
ix. Branch cables are to be secured by PVC insulated clips. These clips shall be attached to the coach body by screws.
x. PVC/FRP Cleats with non-inflammable properties only shall be used.
xi. Wherever cables pass through holes, orifices, slits, apertures etc. with sharp metal edges, such opening shall be provided with fire retardant PVC grommets grade 6.
xii. The cables should be terminated in the junction boxes, terminal boards etc. with lugs.
xiii. The cables should be not have any intermediate joints and should be terminated in junction boxes, terminal boards.
xiv. Laptop/mobile charging points should not be used for Radio, electric shaver or any other appliances.
xv. Locking and securing arrangement for the doors and covers of electrical control/power cubicle and terminal boards should be ensured to prevent unauthorized access to the live parts of electrical equipment.
xvi. There should not be earth leakage one either positive or negative cables.
xvii. All the electrical fittings both on super structure and on under fame shall be mounted directly on the coach body and shall not be electrically insulated.
xviii. All the electrical equipments above 110V shall be individually provided with earthing shunts between equipment body and coach body.
xix. The clearance between live part and coach body should be 10 mm and 4 mm between parts of opposite polarities for 110V system.
xx. The insulating fire retardant low-tension (FRLT) tape should only be used in the coaches. xxi. Coaches, poor joints should not be allowed.
xxii. The IR value should not be less than 2 mega ohms for 110V, 190V, 230V when measured with 500V megger and 3 mega ohms for 415V circuits when measured with 1000V megger.
xxiii. The rewiring of coach should be done after 12 years. However it should not exceed 15 years even if the wiring is good.
xxiv. The battery boxes with LMLA batteries shall be provided with FRP trays at the bottom of the battery box to avoid corrosion of battery box due to spilling of acid. The box shall be provided with ventilating grills and drain pipe to permit the flow of outside air over the cells and to allow spilled acid and water to drain out.
xxv. The battery box shall have minimum 150 mm clearance at the top of the battery for maintenance of cells.
xxvi. The battery box should be painted with two coats of acid resistance paint to protect against corrosion from battery acid.
xxvii. Correct size of fuses and MCBs to be maintained to blow/trip in case of abnormality
xxviii. It should be ensured that the vane relay should work properly. xxix. It should be ensured that the OVP should work properly.
xxx. Fans, berth lights, step lights, tail lights, and side light fittings to be provided with connecters for feeding supply to them.
xxxi. Connectors used in should be made of tough non-ignitable moulding material or rigid PVC.
45. Describe briefly the equipment used in Railway air conditioning coaches.
Compressor:
It has two fold functions. It removes Vapour from the evaporator at a rate, which will permit steady state conditions of temperature and pressure in the evaporator. It discharges the Vapour at a pressure and temperature high enough to permit heat rejection along a descending temperature gradient to the cooling water or air of the condenser
Condenser: It is intended for cooling the hot gas and liquefying under pressure. It may be air cooled or water cooled.
Expansion valve:Is function is to control and regulate the rate of flow of the liquid refrigerant under high pressure and allow it into the evaporator under low pressure.
Evaporator: This constitutes the cooling unit, in which the liquid refrigerant under low pressure evaporates and in doing so, it takes its quota of latent heat, there by cooling the medium surrounding the cooling coil.
Alternator:25 KW alternators are used for RMPU coaches and 18 KW for under slung coaches. These are brushless alternators generates 3-phase AC supply Rectifier regulator unit: His is used to rectify Ac out put of the alternator to DC supply It provides DC supply to the field of the alternator. The DC output voltage and current is maintained within set limits by regulating the DC supply to the field.
Battery:
46. Explain working principle of KEL ALTERNATOR/REGULATORS 25KW 135V with the help of circuit diagram?
Ans. For easy understanding of KEL 25 KW alternator/rectifier regulator circuit diagram, was divided into five sub circuits. They are
1. Power supply circuit
2. Field circuit
3. Voltage control circuit
4. Current control circuit
5. Over voltage Protection Circuit
1. Power supply circuit:
This circuit consists of 3 phase alternator(ALT) fuse F1,3 phase bridge rectifier.(PR). Capacitor bank (C1,C2,C3) and current transformers (CTI to CT3). Three phase AC supply (13,14,15 terminals UVW) produced by alternator is fed to 3 phase bridge rectifier through fuse F1. The bridge is protected against voltage surges by 6 numbers of 0.25 mfd 600V capacitors (C1). One 10 mfd 250V capacitors (C2) and one 10 kpf 500V capacitor (C3) are provided across the bridge for filtering DC output and protection against high frequency surges respectively. Capacitors, C, c and resistors are provided as filter for reducing the ripple content. Three current transformers primaries are connected in series to the alternator supply.
Function: When the field coils are excited and rotor is rotated the variation in reluctance offered by the rotor teeth arrangement causes the flux produced by the field coil to pulsate. This pulsation of flux linked with Ac coils and induces e.m.f in the AC windings. The induced e.m.f. in the 3 phase winding is rectified by the 3 phase bridge rectifier. The bridge rectifier also serves the purpose of maintaining the constant polarity in both the directions of the train and prevents current flowing from battery to alternator, when the coach is stable condition.
2. Field circuit:
Field circuit consists of Magnetic amplifiers (MAI & MA1), field full wave bridge rectifier (D1,D2,D3,D4) and free wheeling diode (D5) and normally closed contact of relay. ET is eliminated and Two Magnetic Amplifier are used to control the field voltage and field current, there by controlling the output voltage and output current. MA has six windings. Two are load windings connected in series to the field circuit. One winding is used for voltage/current control and one more winding used as feed back (gain) winding to boost output voltage whentrain is in slow speeds. Two winding are spare. Free wheeling diode is provided to eliminate the surge voltages produced in the field coil. Cathode of free wheeling diode connected to field positive and anode to field negative.
Two phase AC supply of Alternator given to bridge rectifier through field fuse F2, NC of CR, MA1, and MA2 load windings. Load winding terminals are arranged in such way that, series connected two windings of MA1 and MA2 are included in each half cycle. Load windings 162,17, and 162, 17 are connected in one half cycle and 161,18 and 161,18 are included in the other half cycle. The rectified DC positive is fed to field positive (+EX) of alternator through gain winding 40 and 20 Two gain windings of MA1 and MA2 are connected in series. Rectifier negative (19) of bridge rectifier is connected to field negative (-EX). Freewheeling diode is connected across field terminals (19 and 20) in reverse direction. Function: The purpose of field circuit is to feed rectified DC supply for field for excitation. Two phase supply of alternator is rectified by bridge rectifier. This rectified DC is fed to field winding through gain winding. Free wheeling diode is provided to dissipate energy produced in the field, in other way to eliminate surge voltages produced in the field coil. Load windings are connected in the field circuit to vary the field voltage and current.
3. Voltage control circuit:
This circuit consists of auxiliary rectifier (RT1) voltage detector (DT1) and voltage control winding of magnetic amplifier (10,11) blocking diode(D6). The voltage detector consists of resistance network (R1,R2,R3,).and zener diode D8, potentiometer (RH1) is connected across the resistance R3 to vary the output voltage settings. Voltage detector serves the purpose of providing DC signal to the control winding of MA. Function: When the output voltage exceeds the preset value, the drop across R1 is sufficient to conduct zener diode and allows a DC signal to the voltage control winding of MA.
The DC flux produced in control winding will oppose the AC flux of load winding and increases impedance of the field circuit. This increase of impedance, results in decrease of field voltage and field current 20 thereby decreasing output voltage. This process is continuous to maintain the output voltage constant. The voltage setting can be varied by varying the potentiometer. In ’25 KW KEL RR unit the control winding (10,11) are common for both voltage and current control. Two control windings of MA1 and MA2 are connected in series. Diode D1 is provided to prevent creep age of current from DT2 to DT1
4. Current control circuit:
This circuit consists of 3 phase bridge rectifier (RT2), current detector (DT2), blocking diode (D7), control winding of MA(10 & 11), and secondary o f current transformer (CT1 to CT3) The CT1 to CT3 play important role in the current control circuit. The primary of the CTs connected in series with the 3 phase AC supply. The secondary of CTs connected to 3 phase bridge rectifier (RT2). The output voltage of RT2 connected to current detector. RB1 connected across DC output which acts as burden resistance. Current detector consists of resistance network R4,R5 and R6 and zener diode D9. Zener diode D9 is connected across R4 is in series with blocking diode D7 and control winding of magnetic amplifier (10-11). D2 prevents current from DT1 to Dt2, RH2 is provided across R6 to vary the current settings. Function: The current transformer CT1, CT2 and CT3 senses the current flowing in the 3 phases. The burden resistance RB1 converts current signal into voltage signal. This Dc voltage is fed to voltage detector. The voltage obtained from the secondary of CTs fed to the 3 phase bridge rectifier RT2. When the current delivered by the alternator reaches predetermined value the voltage drop across R4 is sufficient to conduct the Zener diode, thereby sending the control current to magnetic amplifier control winding and increases the impedance of field circuit, thereby decreasing field current/output current. This is a continuous process and maintains output current at present value.
5. OVP Circuit:
It consists of auxiliary rectifier (D13, D14, D15) Zener diodes (Z1-Z2), potentio meter(pot) transistors (T1,T2,T3), relay coil (CR), freewheeling diode (D12) and LED (D18). Function: When the output voltage shoots up more than 150 Volts due to failure in control circuit, the drop across middle terminal of potentiometer and negative will be more than Zener voltage of Z2, zener diode Z2 transistors TR1, TR2, TR3 conducts. The relay energized through R4 and TR3, and field supply through NO (Normally open) of relay coil. At this stage the relay is permanently energized unit the reset push button is pressed at base station by staff. Hence, once, over voltage occurs, the field is permanently cut off in this type of regulators. D12 is provided across relay coil to dissipate energy stored in it. Z1 is reference voltage diode. Glowing D17 indicates normal working. CELLS
47. Explain working principle of cells?
Working Principal of Cells: PbO2+Pb+2HSO4↔2PbSO4+2H2O Discharging PbO2 on (+ve) plate and Pb on (-)ve plates are converted into lead sulphate. In this process, HSO is converted and water is formed. Consequently SPG of electrolyte falls and extents of fall is proportional to Ah taken out. Charging: The chemical process is reversed. PbSO4 on positive plate is converted into PbO2 (lead peroxide) and PbSo4 on negative plate into Pb ( spongy lead ).H2SO4 is formed and water is consumed.SPG of electrolyte rose.
48. What are the types of Batteries used in Indian Railways? Types of Batteries used in Indian Railway:
A. Lead Acid:
1. Conventional type
2. VRLA (Valve Regulated Lead Acid Batteries )
3. Low maintenance Batteries
B. Alkaline Batteries:
1. Nickel Cadmium
2. Silver Zinc Constructional features:
1. Positive Plates
2. Negative Plates
3. Separators
4. Container
5. Cell cover Accessories:
a. Float
b. Float guide
c. Vent Plug Capacities of Batteries In train Lighting:
A.120 Ah-110 v DC, BG, TL coach
B.800 Ah-110 v DC, BG, ACCW AC coach
C.1100 Ah (VRLA)-110 v DC, BG, convention type AC coach
D.120 Ah (VRLA)-110 v DC, BG, TL coach
E.1100 AH (Low maintenance)-110 v DC, RMPU type AC coach.
49. Explain Initial Charging to a new commissioned battery in workshop?
Initial Charging to a new commissioned battery:
Lead Acid Batteries are supplied in uncharged condition without electrolyte. Before using Lead Acid battery, it has to be initially filled with recommended quality and quantity of electrolyte and make ready for initial charging. The whole phenomenon is associated with the following activities:
a. Preparation of Electrolyte
b. Initial filling
c. Initial charging Preparation of Electrolyte:
Initial filling:
50. Explain Trickle Charging of Batteries?
Trickle Charging: When a battery is kept as an emergency reserve, it is very essential that it should be found fully charged when an emergency arises. Due to leakage action and open circuit losses, the batteries deteriorate .Hence to keep it fresh, batteries are kept on a small charging.
For example: A standby battery for station bas-bar of 400 Ah at 10 hr rating, a continuous trickle charge of 1 Amp will keep the cells fully charged and keep in perfect condition.
51. What are the Indications of a fully charged cell?
Indications of a fully charged cell: The indications of a fully charged cell are:
(i) Gassing
(ii) Voltage
(iii) Specific gravity and colour of the plates
(i) Gassing When the cell is fully charged, it freely gives off hydrogen at cathode and oxygen at the anode, the process being known as “Gassing”. Gassing at both plates indicates that the current is no longer doing any useful work and hence should be stopped. Moreover, when the cell is fully charged, the electrolyte assumes a milky appearance.
(ii) Voltage The voltage ceases to rise when the cell becomes fully – charged. The value of the voltage of a fully – charged cell is a variable quantity being affected by the rate of charging, the temperature and specific gravity of the electrolyte etc. The approximate value of the e.m.f is 2.1 V or so.
(iii) Specific Gravity of the Electrolyte A third indication of the state of charge of a battery is given by the specific gravity of the electrolyte. We have seen from the chemical equations of Art.9.9, that during discharging, the density of electrolyte decreases due to other production of water, whereas it increases during charging due to the absorption of water. The value of density when the cell is fully charged is 1.21 and 1.18 when discharged up to 1.8 V. Specific gravity can be measured with a suitable hydrometer which consists of a float, a chamber for the electrolyte and a squeeze bulb.
(iv) Colour The colour plates, on full charge is deep chocolate brown for positive plate and clear slate gray for negative plate and the cell looks quite brisk and alive.
52. What are the Factors affecting the life of Lead Acid Battery?
Factors affecting the life of Lead Acid Battery:
1. Necessity of frequent topping of cells.
2. Leakage of electrolyte on lid and on container body.
3. Failure on one cell on a mono-block unit.
4. Undercharging / overcharging.
5. Always use distilled water for toping of cells.
6. Keeping the discharged cells for long time will result in formation of sulphation.
53. What are the diseases associated with a Lead Acid Batteries and their remedial action?
DISEASE CAUSING TO LEAD ACID BATTERIES OF TL CELLS The diseases are:
1. Sulphation
2. Bucking and cracked plates
3. Loss of capacity
4. Low specific gravity and low voltage of cell
5. Reversed cells 6. Dead cells
7. Loss of active material
8. Sludge
9. Internal short circuit of one or more cells.
SULPHATION: Sulphation means the formation of lead sulphate on the surface and in the pores of the active materials of the plates. Sulphate is finely crystalline and easily reduced by the charging current. Sulphation in this sense is a necessary part of the operation of battery and is not a source of trouble. Lead sulphate is also formed as result of local action or self discharge of the plate. This is brought about by the action of the acid solution on the concentration and temperature of the electrolyte. Lead sulphate formed as a result of local action is easily reduced by the charging current unless it is neglected. Sulphation applies to the large crystals of lead sulphate that may form on the plates as a result of neglect or misuse. Excessive sulphation of this type is difficult to reduce and may injure the plates. The effect is usually noticed by a whitish colour on plates and is caused by over charging, over discharging or keeping the discharged battery for a long time. Carbonate of soda added to the electrolyte has a beneficial effect in preventing sulpahtion defect, or the best way is trickling charge i.e., charging the battery at a low rate for long time.
CAUSES OF SULPHATION
1. Due to over charging
2. Over discharging
3. Impurities in acid, plates, or electrolyte
4. Due to plates are not covered by the electrolyte
5. Due to neglect of battery, Sulphation is caused
6. Kept under discharged condition for long time
TREATMENT FOR SULPHATED CELLS
Light sulphation:- If it is taken in time, charging at low rate approximately 1/3 rd of the normal charging rate will reduce sulphation. The charge should be continued till cells gas freely. Repeat charge and discharge two to three times till specific gravity of 1.220 is reached.
Badsulphation:- Empty the container and fill with distilled water, charge at 1/10th of normal rate and test specific gravity at intervals and it is above 1.150. Stop charging and empty out the electrolyte. Refill with pure distilled water and continue charge. Ensure that the temperature of the electrolyte does not rise above 120 degrees F (49 degrees C). The charge of the sulphate will be indicated by the colour of the plates. After all Sulphation is reduced empty the jar and refill with electrolyte of 1.220 Specific gravity. It is not advisable to use any de Sulphation agents since Sulphation is the natural result of battery action.
54. What are the points to be followed for the Healthy condition of the Battery set?
Maintenance of Lead – acid cells: The following important points should be kept in mind for keeping the battery in good condition:
1. Discharging should not be prolonged after the minimum value of the voltage for the particular rate of discharge is reached.
2. It should not be left in discharged condition for long.
3. The level of the electrolyte should always be 10 to 15 mm above the top of the plates which must not be left exposed to air. Evaporation of electrolyte should be made up by adding distilled water occasionally.
4. Since acid does not vaporize, none should be added.
5. Vent openings in the filling plug should be kept open to prevent gases formed within from building a high pressure.
6. The acid and corrosion on the battery top should be washed off with a cloth moistened with baking soda or ammonia and water.
7. The battery terminals and metal supports should be cleaned down to bare metal and covered with Vaseline or petroleum jelly.
HEALTHY CONDITION OF A CELL/BATTERY
Checking the SPGR of electrolyte. If it is 1.220 the battery are fully charged condition. If it is 1.175 half charged condition. If it is 1.100 it is in fully discharged condition.
1.Checking the voltage of the cell. Switch on lights and fans in coach before taking voltage. Reading as even a discharged cell may show 2volts on open circuit. Now measure the voltage of the cell. The voltage of the fully charged cell on discharge will be about 2volts. When the cell 25 voltage is about 1.85 volts, it should be considered as practically fully discharged and arrangements are made for charging.
55. Write short notes on Hydrometer and cell tester?
HYDRO METER: This meter is used to measure SPGR of liquids. It consists of glass tube with a glass bulb. The glass bulb is fitted with lead balls and is fitted with scale, on which SPGR is marked. This glass bulb is kept in a glass tube. One side of glass tube is fitted with rubber bulb and on the other side a nozzle. The rubber bulb is pressed to suck electrolyte from the battery. The electrolyte enters in the outer glass tube in which hydro meter bulb floats and gives reading. With the dilute sulphuric acid the bulb sinks more in the electrolyte, while with strong sulphuric acid the bulb less. In this way it gives reading to know the performance of battery.
CELL TESTER OR HIGH RATE TESTER
This is a tester which gives the correct terminal voltage on full load of the cell. In the tester there is one resistance of low value which works as load on the cell of the battery. One voltmeter is connected to give voltage. On the same voltmeter dial, charged to discharge conditions are also indicated by the words full charged, half charged and dead. One small lamp is connected in parallel with the voltmeter to indicate light. This tester gives the reading to one cell only at a time. Following precautions are to be taken while using this cell tester.
56. Explain the Salient features of VRLA batteries?
VRLA / SMF batteries The lead acid battery, used in the automobile industry, consists of a spongy lead negative and lead dioxide positive with sulphuric acid as electrolyte. It has a nominal voltage of 2V and requires periodic maintenance, depending on its use. The conventional lead acid battery is improved by developing valve regulated sealed lead-acid battery (VRSLAB) with absorbent glass mat or gel technology. These batteries need no addition of water during their normal life time. There is no spillage of electrolyte or release of gas. The batteries are charged by constant potential mode. Calcium alloys are used as grid material due to their lower self-discharges and increase conductivity. Oxygen and hydrogen evolve from positive and negative respectively during recharge. Oxygen evolved at the anode reacts with the hydrogen through the separator to produce water. A valve releases the excess gas, preventing accident during overcharging. VRSLAB finds usage in electronic equipment, standby systems and remote area power supplies where solar power is used to charge batteries.
57. What are the main parts of the VRLA batteries?
Parts of VRLA Batteries
1. Positive plates: Flat pasted type with lead-calcium High Tin alloy or lead cadmium alloy to resist corrosion & for longer life.
2. Negative plates: Flat pasted type with lead-calcium alloy grid for maintenance free characteristics. 3. Separator: Low resistance, high porosity and highly absorbent glass mat separator (AGM)
4. Electrolyte: High purity Sulphuric acid to maximize shelf life
5. Terminals: High conductivity lead plated inserts.
6. Safety Valve: Self resealing, pressure regulated and explosion proof.
7. Container and Cover Sealing: Heat Sealing Method (Fusion bond) for better joint strength 8. Container: High impact Polypropylene co-polymer
58. Explain Working principle of VRLA batteries?
Working principle of VRLA batteries Valve Regulated Lead Acid (VRLA) batteries can be of either the gelled electrolyte type or the absorbed electrolyte type, While the basic electrode reactions remain the same as in conventional flooded cells, VRLA batteries operate on the oxygen recombination principle. Due to the special grid alloys used, the actual gas evolution is 97% less than in conventional batteries. The conventional flooded batteries, oxygen evolved at the positive plate bubbles upwards through the electrolyte and is released through the vent plugs. In VRLA batteries, however, the small amount of oxygen that is evolved, is transported through the separator to the negative plate via the gas phase, and is consumed at the negative plate. Special features of VRLA batteries
FEATURES:
VRLA batteries using absorbed electrolyte have the following special features.
1. Starved electrolyte The electrolyte is immobilized by using highly absorbent glass mat separators which are designed to hold sufficient electrolyte to meet all performance requirements. Oxygen Recombination The battery works on the oxygen recombination principle. Recombination efficiencies are in excess of 99%. Explosion resistant safety vents VRLA batteries operate at a slight positive pressure within the cell. Cells are fitted with a unique low pressure self resealing safety vent plug which releases the gasses when the internal pressure within a cell exceeds 6 PSI and reseals again at low pressures. The constant positive pressure in the cells prevents accidental ingress of external air which would otherwise result in self discharge at the negative plate. The vent plugs are also fitted with a porous plastic disc, which prevent external sparks from entering the cell. This makes the vent plug explosion proof. Hermetic Heat Seal The battery jar & cover are hermetically sealed on automatic machines. Additionally, the total absorption of electrolyte in the separators and the use of pressure regulated vents make it spill proof and leak proof. Superior alloys VRLA batteries use highly corrosion resistant alloys such as Lead cadmium resistant lead alloys. Copper insert terminals VRLA batteries have highly conductive copper inserts in terminals resulting in very good power characteristics. Inter cell connections are done by using high purity lead coated copper strip connectors and heavy duty stainless steel bolts which are resistant to sulphuric acid. Modular Steel Trays VRLA batteries are assembled in modular steel trays normally in the horizontal configuration .This lends flexibility in assembling the system one module above the other.
59. What are the advantages of VRLA batteries over conventional flooded tubular batteries?
Advantages of VRLA batteries In Railway applications such as train lighting and air conditioning etc., VRLA batteries have marked advantages over the conventional flooded designs. Some of these advantages are given in the following comparison table: Conventional Flooded Batteries VRLA Batteries
1. Regular maintenance required involving topping up with distilled water.
2. A lot of excess free acid is available leading to acid stratification. This is more pronounced in taller cells. 3. There is a possibility of ground currents due to electrolyte spillage. This can result in high rates of self discharge.
4. Batteries are housed in MS boxes under the coaches.
5. There is a possibility of shedding of active material due to vibration in service.
6. These batteries are mounted vertically hence the ‘g’ force acting on the cell is high.
7. Post corrosion is usually observed due to the acid mist.
8. Cover sealed by bitumen to hard rubber container. Cracking and debonding of the sealing compound is a very common problem.
9. Self discharge rate up to 4% of capacity per week.
10. The average discharge voltage is 1.90VPC.
1. No periodic topping since this battery work on the oxygen recombination reaction resulting in zero loss of water.
2. No stratification of electrolyte because of the wicking action of the absorbent separators. The cells are mounted horizontally reducing the height of cell. Stratification is there fore eliminated.
3. There is no possibility of electrolyte spillage due to the dry leak proof construction hence ground currents are eliminated.
4. The VRLA battery unit can directly bolted horizontally to the under carriage of the coach. This will eliminates the need for battery boxes as well as the FRP trays used in existing designs.
5. Due to the highly compressible glass mat separators, the possibility of shedding of active materials is minimized. Hence VRLA batteries exhibit batter vibration resistance.
6. VRLA batteries are mounted horizontally reducing the ‘g’ force acting on the cells.
7. No post corrosion since there is no acid mist.
8.Cell covers and jars are hermetically heat sealed. No operational problems envisaged.
9. Very low self discharge of 0.5 to 1.0 % of capacity per week.
10. VRLA batteries have good voltage. The average discharge voltage is 1.95 VPC resulting in lower battery currents. There is therefore less heating and wear & tear of electrical components. The discharge plateau of VRLA batteries is also flatter
11. Transits damages are high because of brittle rubber containers.
12. Separate battery room and charging at site is required. This increases the time and space requirements for battery charging. leading to uniform intensity of light bulbs, for longer duration. 11. VRLA batteries are housed in steel trays which can withstand drops and shocks during transit. Hence transit damages are virtually eliminated.
12. These batteries are factory charged . Commissioning is immediate. A 80% savings installation time is quite common. Further , the requirements of a separate battery room and charger are considerably reduced.
60. Explain the procedure for the POH of VRLA cells in workshop.
Procedure to be followed in Workshop during POH: The below given instructions are to be followed when the coach comes for periodic overhaul { POH } to the workshop.
1. Remove all the cell terminal bolts, Flat washers, spring washers, inter cell cables, connectors etc. {use insulated tools only}
2. Care should be taken to avoid any shorting of cell terminals while removing inter cell cable connectors.
3. Remove the stacking bolts used for fixing battery modules to battery box/ cradle and between the trays.
4. Remove the modules with batteries from battery box/ cradle by using suitable tool.
5. Clean all the cell terminal posts and inter cell connectors/ cable lugs with a brass wire brush to remove any sulphated layer.
6. Refix the inter cell connectors/ cables and tighten the bolts along with flat and spring washers to specified torque. Replace old spring washers 100%. Quality of new spring washers should be checked as per IS 3063 especially permanent set test.
7. Discharge the battery bank at the rate of 0.1C and by pass each cell whenever it reaches end cell voltage of 1.75V.
8. Charge the cells at 7% constant current {77 Amps for 1100 Ah and 8.4 Amps for 120 Ah} for 15 hours.
9. Again give rest to the cells for 6-8 hours.
10. Discharge the cells at 12 Amperes for 120 Ah and 110 Amperes for 1100 Ah gradually by passing each cell whenever each cell reach 1.75 V. Duration of discharge shall be recorded. If the discharge duration of the cells is found to be more than 8 hrs these can be put back in service after charging.
11. If the cells do not give more than 8 hrs of discharge duration before reaching end cell voltage of 1.75 V, repeat this charging and discharging cycle once more. Cells should not be discharged below 1.75V .
12. Even then, if the cells do not give more than 8 hrs then the cells shall not be put in service.
13. Clean and repaint the modules/ cell trays. These may be numbered with the help of stenciling to identify the modules consisting of a battery set for a coach { say Module No / Set No. e.g. 08 /01 means 8th module of Set No. 1} . The other details like cell number, date of manufacture as indicated on the cell lid and date of fitment shall also be recorded to monitor age-wise performance of the cells.
Note: All the new VRLA cells shall be given a boost charging if the cells have been lying in the Depot / workshop for more than 6 month period from the date of manufacture.
QUESTION BANK FOR TRAIN LIGHTING COACHES
1. On what factors the output voltage of TL/AC alternator depends on?
Ans. The output voltage of TL/AC alternator depends on, speed of the rotor and level of field excitation.
2. Write about the working principle of TL/AC alternator?
Ans. The core of the stator which is completely embraced by the field coils will retain a residual magnetism if excited by a battery once. The flux produced by the filed coils find its path through the rotor. When the rotor is rotated the passage of rotor teeth and slots, alternatively, under the field, offers a varying reluctance path for the flux produced by the field coils. The flux, which varies periodically, links with AC coils and induces an alternating voltage in AC coil. The frequency of the induced voltage depends on the speed of rotor, where as the magnitude depends on the speed of the rotor and the level of excitation. The field is controlled through regulator to attain desired output voltage by means of positive feedback again.
3. What are the reasons for loss of residual magnetism? How do you regain it? What is the permissible and maximum DC voltage is to be applied to regain the residual magnetism?
Ans. The reasons for los of residual magnetism are keeping the alternator in idle condition for long time and connecting field wires in wrong polarity. To regain the residual magnetism flash the field terminals for correct polarity of DC supply. The permissible DC voltage is to be applied to regain the residual magnetism is 6 to 12V DC. Maximum voltage is 24V DC.
4. Explain the capacities of alternators used in TL/AC coaches?
Ans: The capacities of Alternators used in TL/AC coaches are
1. Train Lighting 110V system = 4.5 KW 130 Volts
2. Air Conditioning 110V BG coaches under slung = 18 KW 135 Volts
3. Air Conditioning 110V BG RMPU coaches = 22.5 KW 135 Volts = 25 KW 135 Volts
5. What is the purpose of belt-tensioning device? What are the parts it consists of?
Ans. The purpose of belt tensioning device is to keep V belts in tight condition. Its parts are
1. Tension rod
2. Tension spring
3. Belt tension indicator with spring seat
4. Fork eye
5. Fork eye side spring seat
6. Belt tightening nut 7. Free end pipe and nut
61. Explain working principle of KEL ALTERNATOR/REGULATORS 110 V, 4.5 K.W with the help of circuit diagram?
Ans . For easy understanding of KEL 3 & 4.5KW 30 volts alternator/rectifier regulator circuit diagram, was divided into four sub circuits. They are
1. Power supply circuit
2. Field circuit
3. Voltage control circuit
4. Current control circuit
1. Power supply circuit: This circuit consists of 3 phase alternator (ALT) & 3 phase bridge rectifier.(PR). Three phase AC supply (13,14,15 terminals) produced by alternator is fed to 3 phase bridge rectifier consists of 6 silicon power diodes. The bridge is protected against voltage surges by 6 numbers of 0.25 mfd capacitors (C1 to C6), One 10 mfd capacitor (C7) and one 10000pf capacitor (C8) are provided across the bridge for filtering DC output and protection against high frequency surges respectively. Shunt (26 amd 28) is provided in series to DC output voltage positive (+L) terminal,for sensing output current. DC output voltage terminals are(+L,-C) Function When the field coils are excited and rotor is rotated the variation in reluctance offered by the rotor teeth arrangement causes the flux produced by the field coil to pulsate. This pulsation of flux linked with Ac coils and induces e.m.f. in the AC windings. The induced e.m.f. in the 3 phase winding is rectified by the 3 phase bridge rectifier. The bridge rectifier also serves the purpose of maintaining the constant polarity in both the directions of the train and prevents current flowing from battery to alternator, when the coach is stable condition.
2. Field circuit: Field circuit consists of Excitation transformer (ET) Magnetic amplifier(MA),. Field rectifier (D2,D3) and Free wheeling diode(D4). And ET is an auto step up centre tapped transformer. It has three functions. 1. It is auto transformer having one winding 2. It steps up the voltage for good regulation of output voltage and current.
3. Its secondary winding is centre tapped used for full wave rectification with two diodes and accommodates load windings of MA. Magnetic Amplifier is used to control the field voltage and field current, there by controlling the output voltage and output current. It has six windings. Two are load windings connected in series to the field circuit. One winding is used for voltage control and one more winding is used for current control and other winding used as gain winding to boost output voltage when train is in slow speeds one more winding is spare. Free wheeling diode is provided to eliminate the surge voltage produced in the field coil. Cathode of free wheeling diode connected to field positive and anode to field negative. Two phase AC supply of Alternator given to ET primary (14 & 15 terminals) through field fuse F2. The centre tap secondary terminals (19) is connected to field negative (-EX) of alternator. The end terminals of ET secondary ( 18 &161) are connected to full wave rectifier (D2 &D3) through MA load windings (18,162 and 161,17). The rectified DC fed to field positive (+EX) of alternator through gain winding. (40 and 20). Free wheeling diode is connected across field terminals (19and20) in reverse direction. Function: The purpose of field circuit is to feed rectified DC supply for field for excitation. Two phase supply of alternator is stepped up by ET and rectified by full wave rectifier. This rectified DC is fed to field winding through gain winding. Free wheeling diode is provided to dissipate energy produced in the field, in other way to eliminate surge voltages produced in the field coil. 3. Voltage control circuit: This circuit consists of auxiliary rectifier(RT) (D5,D6,D7), voltage detector (DT) and voltage control winding of magnetic amplifier(10,11). The voltage detector consists of resistance network (R1,R2,R3,R4) and zener diode D8, 1k potentiometer (RH) is connected across the resistance R4 to vary the output voltage settings. Voltage detector serves the purpose of providing DC signal to the control winding of MA. Function: When the output voltage exceeds the present value, the drop across R1 is sufficient to conduct Zener diode and allows a DC signal to the voltage control winding of MA. The DC flux produced in control winding will oppose the AC flux of load winding and increases impedance of the field circuit. This increase of impedance, results in decrease of field voltage and field current there by decreasing output voltage. This process is continuous to maintain the output voltage constant. The voltage setting can be varied by varying the 1k potentio meter.
4. Current control circuit: This circuit consist of shunt resistance (SHR 26,28 terminals) shunt diode(D1) and current control winding of M.A(26and27). For sensing output current, SHR is provided in the DC output voltage of alternator. Shunt leads are connected to MA current control winding through shunt diode.
Function: When preset value of current is supplied by the alternator exceeds, the voltage drop across the shunt is sufficient to conduct shunt diode. When shunt diode conducts, it sends a DC signal to current control windings of MA. This DC signal induces DC flux in the windings. This Dc flux opposes the AC flux of load windings and increases the impedance of the field circuit. Increase of impedance in field circuit reduces the field voltage and field current there by decreasing the output voltage and output current. This process repeats when the output current exceeds and maintain the alternator current within preset limits. The current setting can be varied by varying the shunt resistance.
62. What are the precautions to be taken while loading and unloading of alternator?
Ans. i) While unloading and loading alternator, see that the terminal box and pulley should not be broken.
ii) The alternator to be loaded in correct way that bushes to be provided in proper place.
iii) While loading and unloading proper precautions to be taken not to fall on ground otherwise men/materials will be injured/damaged.
iv) See that the anti rotating clamp provided on trolley coincides with alternator suspension pin.
v) Replace the worn out alternator and alternator suspension bracket bushes.
vi) See that the alternator should not have play with proper washers in improper place to align the axle pulley.
vii) Safety chains and cotter pins to be provided without fail.
63. What are the Rating of various fuses in TL coach wiring system?
Ans. Main Battery Fuse is 40 A. L1,L2, Fan and EFT circuit fuses are 16 Amps HRC Main Negative fuse is of 35 amps HRC And Branch fuses are 35 SWG
64. What are the main components of Lead Acid cell?
Ans. Main components of Lead Acid cells are:
a) Positive Plates, which are tubular n shape, made of PBO2
b) Negative Plates, usually consists of lead grid into which active material of Sponge lead is pressed. c) Separators, which are made by Synthetic, used between Positive and negative plates.
d) Container is made of hard rubber or PPCP with high insulating strength to resist acids which are used as Electrolyte.
e) Cell cover which covers container having vent plugs and level indicator.
65. What is the Specific Gravity of fully charged lead acid cells?
Ans. The specific gravity of fully charged cell is in between 1.210- 1.220
66. What is meant by PPCP container?
Ans. Some cell container are made of PPCP which is called Poly Propylene Co-Polymer.
67. What is the SWG of DFB fuse?
Ans. The size of fuse wire 35 SWG is provided in Distribution Fuse board for each fan or light.
68. What is the wattage of 400 mm 110 V DC fan?
Ans. The Wattage of 400 mm DC fan in TL Coach is 35 Watts.
69. What is the specific gravity of sulphuric acid?
Ans. The specific gravity of sulphuric acid which is used to make electrolyte is 1.835.
70. What is the working voltage of 20 W/18W TL inverter?
Ans. The working voltage of 20W/TL inverter is 110 volts D.C.
71. What procedure is adopted to detect Earth leakage in a TL coach?
Ans. Double test lamp method.
72. Enumerate the cable sizes used in TL coaches?
Ans. Branch wiring : 4sq.mm Aluminium. LI,LII, and F+ve: 16 sq.mm Aluminium SPMI&II: 16sq.mm Aluminium Under frame wiring: Alternator to regulator Field winding -6sq.mm copper Main windings-16 sq.mm copper Regulator to under frame junction box: 35 sq.mm Al. UFJB to Battery box: 35 sq.mm Al
73. What is the maximum permissible voltage drop in TL coach?
Ans. The maximum permissible voltage drop allowed between the battery and any of the farthest light/fan point shall not exceed 3 volts at battery voltage of 108 +0/-2 volts.
74. What is the insulation tape used for insulation of cables in TL &AC coaches?
Ans. Flame retardant low-tension tape. 75. What method of charging is used for Lead acid cells and VRLA cells during POH? Ans. Constant current method of charging is adopted.
76. Give important measures adopted by railways for prevention of fires in TL coaches?
Ans. a) Cable sizes have been standardized.
b) Provision of re-wirable fuse on both positive and negative side in the distribution fuse board
c) Use of self extinguishing PVC cables.
d) Provision of rubber grommets at points where the cable enters through metal members in the coach.
f) Proper crimping at the cable terminals.
g) Air clearance of 10 mm between live part and earth and between parts of opposite polarity.
h) Replacing of cables with any joints, noticed during POH.
i) Re-wiring of the coach planned on the basis of cable life of 20 years.
j) Use of Flame retardant Insulation tape.
k) Checking of coach wiring by double test lamp method.
77. What precautions will you take during re-wiring of a coach?
Ans. a) Use of PVC cables of suitable current.
b) In under frame and end walls of coach the wiring has to be drawn through Rigid steel conduits
c) Use of proper size of fuses.
d) The phase and field wires from the Alternator to terminal box shall be run in one flexible PVC conduit and from terminal box to rectifier – cum-regulator & from rectifier-cumregulator to under frame terminal board in one rigid steel conduit.
e) Proper method of crimping by using proper die and use of corrosion inhibiting compound during crimping of Aluminium cables.
f) Segregation of positive and negative cables. g) Cables in the roof (super structure) to be carried in non-metallic rigid conduits with proper cleating arrangement.
h) Use of FRLT insulation tape.
i) After re-wiring the test the insulation resistance with 500v dc megger. The minimum insulation resistance should be 2 Mega ohms.
24. Procedure to maintain correct tension of new ‘V’ belts on bogie transform mounted alternator of AC Coaches and non AC coaches.
Ans. 1. Provide alternator on the bogie.
2. Provide axle pulley on the wheel.
3.Provide ‘V’ belt of matching set between grade 48 & 52 on wheel axle, on which, the axle pulley is provided.
4. After lowering and completion of buffer head adjustment of bogie, provide ‘V’ belts over alternator towards the axle pulley.
5. After completion of provision of V belt, remove the split pin check nut and fixing nut of free end side tension rod spring tightening collar nut.
6. Free the check nut and fixing nut of U clamp side of tension rod.
7. Now insert the tension rod assembly between the bogie supporting bracket and eye (leg) of the alternator.
8. Provide bolt for ‘U’ clamp of tension rod and eye of the alternator.
9. Then slowly tighten the fixing nut (U clamp side) unit tension indicator match with the spring collar. This will give the correct tension of the V belt.
10. Then provide fixing nut, check nut and split pin leaving a gap of 75 mm for AC coaches and 55 mm non AC coaches at free end side of tensioning for mechanism.
11. Then observe the tension of belt.
25. What are the advantages and disadvantages of 110 Volts DC Train lighting System?
Ans. Advantages:
1. The demand for better passenger amenities like improved illumination, provision of tube lights with inverters, provision of water coolers/refrigerators can be achieved in this system.
2. For the same loads, the current handled is only 21.8% therefore cables and connectors are smaller in size.
3. The ratio of short circuit current and the normal full load will be high. Therefore faults discrimination better in 110 V systems.
4. Florescent lights can be used with the aid of electronic invertors (without choke and bulb).
5. Higher coach loads can be handled with the higher generation capacity to meet the additional amenities like. Provision of fluorescent lamps in sleeper coach. Provision of more fans in sleeper and GS coaches. Provision of water coolers in coaches etc. Due to current flowing in the circuits is low the voltage drop reduced to minimum the illumination in the coaches is improved.
6. In the 110V DC system, the size and weight of the cells reduced considerably easy to handle.
7. Bogie transform mounted alternators with V belts are provided to avoid theft of belts and alternator parts.
Disadvantages:
1. In the 120 volts system single battery is provided load on the battery is more. The life of the battery is reduced considerably.
2. Due to introduction of transform mounting system the complete coach has to be lifted for replacement of V belts.
3. Due to provision smaller size batteries, the quantity of electrolyte is limited. If the level of electrolyte is not maintained by adding distilled water, the batteries may damage.
4. Due to high voltage system, requires high value of insulation resistance for safety etc.
26. What are the major train lighting equipment available in Self Generating coaches and explain about them briefly?
Ans. The major train lighting equipment in coach are
1. Alternator
2. Rectifier cum Regulator Unit
3. Battery
4. Axle Pulley
5. Rotary/ Roof Junction Box
6. Under frame Junction Box
7. Fans
8. Lights
9. EFT
10. BCT
27. Draw the schematic diagram of 110 Volts DC TL system including capacities of equipment and protective devices?
Ans. Schematic diagram of 110 v DC TL system Major Equipment: Alternator 4.5 kw R R U 110 V DC 32A 120 Ah BCT R/S 40A 16 A L-1 L-2 F-1 SPM RJB (+)FDB 6A 6A - ve fuse 35 A (-) FDB - ve + ve
Alternator - 4.5 kw, 110V, 3 phase, brush less type, totally enclosed, reversible shunt wound.
Regulator Board (RRU/ERRU) - 4.5 kw.
28. Draw the neat Coach Wiring Diagram of 110V DC TL system including capacities of equipment and protection devices? Diagram Of 110 Volts DCTL System Including Capacities Of Equipment And Protection Devices
MAJOR EQUIPMENTS IN TL COACH:
PROTECTIVE DEVICE:
29. What are the sizes / capacity of fuses provided at various locations of 110 Volts Train Lighting coach? Ans. Sl. No. Circuit fuse Location Fuse size Current rating 1. 2. 3. 4. 5. 6. 7. Positive/negative SPM1 & SPM2 Main negative L1, L2, and F +ve Battery fuse Field fuse AC fuse Branch fuses Junction box J/Box J/Box Battery box Regulator box Regulator box DFB 35 SWG RW 16A HRC 35A HRC 16A HRC 40A HRC 6A HRC 20 35A HRC 6A --- --- --- --- 6A --- ELECTRONIC RECTIFIER CUM REGULATOR UNIT (ERRU)
30. What are the advantages and disadvantages of ERRU? Advantages of ERRU:
1. Control circuit is Modular type design.
2. Auto identification of alternator ratings and indications.
3. Auto setting of parameter of voltage, load current, Battery current, over voltage, over current and current limiting for all the regulator of 4.5 kw, 18kw and 25kw.
4. UVC is interchangeable with all types of electronic regulators from 4.5 kw to 2.5 kw.
5. Close regulation of voltage +/-2 V over the entire range of load and speed to have uniform charging of batteries.
6. Less voltage and current ripple on Battery Charging current.
7. Controlled battery charging current to have longer life of batteries.
8. Moduled Hall sensors for current sensing and setting current limit.
9. Static over voltage protection and latching without battery.
10.Isolated power packs directly mounted on the heat sinks to have better heat dissipation. 11.Moulded PCBs to avoid dust and vibration problems.
12.Separate interface unit for monitoring the parameters like DC Voltage, DC current, Battery charging and discharging currents, Amps Hours etc.
13.This interface facilities to store AH.IN and AH.OUT. generation and non-generation time, total distance travelled by coach and faults occurred in the regulators.
14.This interface also has Emergency unit. In case of failure of one control unit, the other control unit will take care of both regulators.
Disadvantages of ERRU:
1. Sophisicated electronic equipment.
2. Qualified staff are required for maintenance.
3. Costlier than MA type regulator.
4. If PCB failed entire PCB to be changed.
5. For repairing ERRU on test bench, Alternator supply must be required.
6. Alternator setting can not be adjusted manually on test bench.
7. Costlier spare parts are to be stocked.
31. What are the important parts of ERRU? Important parts of ERRU:
1. Iso pack power diodes
2. Universal voltage controller
3. IGBT controlled field circuit
4. Hall sensor
5. Static over voltage protection
6. Interface unit
7. LED/alpha numerical display
Universal Voltage Controller (UVC): This is an electronic controller unit having microprocessor/micro-controller/PWM controller which is common for all ratings i.e.25KW/18 KW & 4.5 KW of alternators and respective ERRU having different power circuits. UVC should be able to identify the rating of the alternator and automatically adjusting the setting parameter as per this specification according to the rating of the alternator and battery. The UVC controls the field current to maintain the set output voltage of the alternator. The field circuit is provided with IGBT. The gate of the IGBT is controlled by micro-controller, which is programmed with all data as per the requirements of the specification. UVC gets the power from power supply modular. Universal Voltage Controller shall be equipped with micro processor/ micro controller/ PWM controller to meet the various requirements laid down. Wherever possible, adequate design redundancy to take care of controller failure from total system failure/hanging. The design of every UVC shall have provision to ensure proper load sharing between two alternators provided on the same AC coach and the difference of load sharing shall not be more than 10A enabling to achieve high reliability of alternators avoiding continuous overloading of one alternator. There shall also be a provision of communication between two ERRU running in parallel. The UVC of ERRU of different rating i.e. 4.5 KW and 215 KW shall have universal application with a common design to achieve inter changeability among the same make. The manufacturer shall have to declare their design and its capacity. The UVC shall be suitable to work with 25 KW & 4.5 KW capacity alternators in the existing field conditions. UVC shall preferably have following features for improving reliability.
UVC shall preferably equipped with minimum of 16 bit industrial micro process/ micro controller with built in USB and PWM control ports.
No through hold type of micro processor/micro controller should be used for high reliability.
External programmed memory should not be used with micro processor/ micro controller for highest reliability of memory fetching.
The PCB design of UVC shall be done only on single card to eliminate the inter connection between PCB and easy service on card replacement basis.
Only sealed membrane key pads should be used along with UVC for highest reliability.
The discrete power supply for powering the UVC micro processor / micro controller must be electrically isolated from coach battery DC power. Following indication shall be available on UVC / display unit in case of 4.5 KW whereas for 25 KW ERRU on UVC and CIP.
Capacity of alternator
Healthiness of UVC IGBT’s used in field circuit:
IGBT : Insulated Gate Bi-polar Transistor – a semi conductor devices used as switching ‘on’ and ‘off’ to control DC input signal to the field for regulating DC output in ERRU. IGBTs are semi conductors that combine a high voltage and high current bipolar junction transistor (BJT) with low power and fast switching metal oxide semiconductor field effect transistor (MOSFET). Consequently IGBTs provide faster speeds, better drive and output characteristics than power BJTs and offer high current densities than equivalent high powered MOSFETs.
Over Voltage Protection in ERRU: OVP: Over Voltage due to component failure/ open circuit in regulator, over voltage protection circuit should be provided with no nuisance tripping under no-load or load condition. During sudden throwing of load (without battery connected) the over voltage relay may, over voltage protection circuit should be provided with no nuisance tripping under no-load or load condition. During sudden throwing of load (without battery connected) the over voltage relay may trip but must reset by itself automatically. Latching of the relay may be achieved under fault condition with battery supply available at the DC output. Certain time delay may be provided for relay operation so that the relay does not trip when load is thrown off suddenly with battery connected. However the time delay provided should be less than 2 sec. in order to protect the system under genuine fault conditions. The tripping voltage of the relay may be set between 138+- 1 volts. Software OVP shall be at 138+- 1 volts where as separate OVP shall be set at 141 +- 1.
LED / alpha numerical display used in ERRU: The UVC shall also be provided with an indication board with LED/ALPH-numerical display to indicate its various status as given below.
1. Capacity of alternator 2. Healthiness of UVC (failure status)
3. Over voltage protection
4. Functional status under emergency
5. Alternator failure
6. Fuse failures phase/ control
7. Overload/ Short circuit
8. Battery charging/ discharging Ah over a duration
42 OBJECTIVE TYPE QUESTIONS MULTIPLE CHOICE ON AIR CONDITIONING SYSTEM
1. The cooling coil in AC system is called
a) Evaporator
b) Condenser
c) Both (a) and (b) d) None
2. The accepted humidity for human comfort is about
a) 40-60% b) 80-100% c) 20-40% d) None
3. The accepted temperature for human comfort during summer is
a) 72°F to 78°F
b) 62°F to 68°F
c) 82°F to 88°F
d) 52°F to 58°
4. The accepted temperature for human comfort during winter is
a) 72°F to 78°F
b) 62° c) 82°F to 88°F
d) 52°F t
5. The purpose of condenser used in vapour compressor system is a) It controls the rate flow of high pressure refrigerant liquid b) It allows refrigerant liquid to evaporator at low pressure c) Both (a) and (b) d) None
6. The purpose of de-hydrator and filter used in vapour compressor system is a) It removes moisture available in refrigerant system b) It prevents particles and scales in refrigerant system c) Both (a) and (b) d) None
7. The danger for the human body, if the temperature falls below
a) 98°F
b)98.6°F
c) 105.6°F
d)None
8.The temperature of air recorded by a thermo meter, when it is not affected by the moisture present in it, is called
a)Wet bulb temperature
b)Dry bulb temperature
c)Dew point temperature
d)None of those
9. Evaporator changes the low pressure liquid refrigerant into
a) High pressure liquid refrigerant
b)Low pressure vapour refrigerant
c) Very high pressure liquid d) None
10. During a refrigerant cycle, heat is rejected by the refrigerant at
a) Compressor
b)Condenser
c)Evaporator
d)Expansion valve
11.Psychometric chart shows relationship between
a) Dry bulb temperature
b) wet bulb temperature
c) Dew point temperature
d)Humidity
e) Total heat (enthalpy)
f) All of the above
12. The purpose of air condition is
a) Temperature control
b) Humidity control
c) Air movement and circulation
d) Air filtering, cleaning and purification
e) All of the above
13. The unit for the capacity of air conditioning is in
a)Ton of refrigeration
b) Kilograms
c) Founds d) None
14. One ton of refrigerant is equal to
a) 3000 Kcal/hour
b) 12000 BTU/hour
c) Both (a) and (b) d) None
15. The cooling in the coach is not sufficient, the reasons may by
a) Compressor not getting loaded/poor efficiency
b) Too little gas or air may have accumulated in the system
c) Condenser, fresh/return filters, evaporator dirty/choked
d) Setting of expansion valve disturbed e) All of the above.
16. Excessive cooling in the coach is due to
a) System working continuously due to fault in the control system b) System kept in manual cooling
c) Compressor defective
d) both (a) and (b)
17. The function of capillary tube is same as
a) Condenser
b) Evaporator
c) Compressor
d) Expansion valve
18. RMPU means
a) Roof mounted package unit
b) Rail mounted package unit
c) Rack mounted package unit
d) None
19. Refrigerant is used in RMPU is
a) R.22
b) R.12
c) R 134a
d) None
20. Chemical name of R.22 is
a) Monochloro difluoromethane CHCIF2
b) Dichloro diflouro methane CCl2F
c) Dichloro monoflouro methane CHCl2F
d) None
21. Quantity of Refrigerant to be charged for one AC circuit of RMPU is about
a) About 3kgs
b) About 20kgs
c) About 30kgs
d) None
22. Power supply is fed to compressors and condenser and evaporator units of RMPU coach is
a) 1 phase 230 v
b) 3 phase 415 V
c) 3 phase 110 V
d) None
23. Capacity control of RMPU is
a) 50% to 100%
b) 25% to 100%
c) 75% to 100%
d) None
24. Capacity in tone of refrigeration of one RMPU has
a) 14tons
b) 5.2 tons
c) 7tons
d) None
25. The power required for one RMPU is about
a) 13 KW
b) 5.75KW
c) 23 KW
d) None
26. The current taken by the one RMPU unit is
a) 40A
b) 22 A
c) 10 A
d) None
27. The capacity of compressor motor used in RMPU AC coach is
a) 5.25 KW
b) 5 .3 KW
c) 4.3 KW
d) None
28. The capacity of condenser motor used in RMPU AC coach is
a) 1 HP
b) 1.5 HP
c) 2.5 HP
d) None
29. The capacity of evaporator fan motor of RMPU AC coaches
a) 1.5 HP
b) 0.5 Hp
c) 2.5 HP
d) None
30. Heater load of one RMPU is about
a) 6 KW
b) 3KW
c) 12KW
d) None
31. Current taken by one compressor motor of RMPU AC coach is
a) 8.25+/-25%
b) 2.6+/-10%
c) 2.2+/-10%
d) None
32. Speed of the condenser motor of RMPU coach is
a) 910 RPM
b) 720 RPM
c) 2880 RPM
d) None
33. Speed of the evaporator fan motor of RMPU coach is
a) 1415 RPM
b) 720 RPM
c) 2880 RPM
d) None
34. The capacity of inverters used in RMPU coach is
a) 18KVA
b) 25KVA
c) 12KVA
d) None
35. Motors used in RMPU coaches are
a) Induction motors
b) Synchronous motors
c) Slip ring induction motors
d) None 36.HP cut out of RMPU
coach shall be set at
a) 135+/-15% PSI
b) 415 +/-15%PSI
c) 35 +/- 15% PSI
d) None
37. LP cut out of RMPU coach shall be set at
a) 135+/-15% PSI
b) 415 +/-15%PSI
c) 35 +/- 15% PSI
d) None
38. The OHP thermostat shall be set to operate at
a) 200°C
b) 150°C
c) 100°C
d) None
39. The cooling temperature settings of electronic thermostat are recommended by RDSO is
a) 23°C,25°C
b) 22°C,25°C
c) 24°C,26°C
d) None
40. The heating temperature settings of electronic thermostat are recommended by RDSO is
a) 17°C,19°C
b) 19°C,21°C
c) 21°C, 23°C
d) None
41. Number of vane relays required for one RMPU are
a) 2
b) 1
c) 4
d) None
42. Capacity of WRA used in RMPU coaches
a) 0.5 HP/0.37 KW at 415 V, 50 HZ,PF 0.5
b) 1.0 HP/0.746 KW at 415 V, 50 HZ, PF 0.5
c) 1.5 HP/1.1 KW at 415 V, 50 HZ PF 0.5
d) None
43. The capacity of control transformer provided in RMPU AC coach is
a) 400 VA
b) 1000 VA
c) 2500 VA
d) None
44. The duration of TDRI delay setting is
a) 2 min
b) 2.5 min
c) 3.5 min
d) None
45. The duration of TDRII delay setting is
a) 2 min
b) 2.5 min
c) 3.5 min
d) None
46. Over load setting range of blower motor of RMPU
a) 0.8 to 1.4 A
b) 1.5 to 2.5 A
c) 7 to 10.5 A
d) None
47. Over load setting range of condenser motor 1 & 2 of RMPU
a) 0.8 to 1.4 A
b) 1.5 to 2.5 A
c) 7 to 10.5 A
d) None
48. Over load setting range of compressor motor 1 & 2 of RMPU
a) 0.8 to 1.4 A
b) 1.5 to 2.5 A
c) 7 to 10.5 A
d) None
49. The purpose of auxiliary contactor AC1 provided in control panel of AC coach is
a) To switch on control supply to condenser motors I & II
b) To switch on control supply for compressor motors I & II
c) To switch on control supply to heaters I & II
d) To switch on control supply to entire control circuit except blower circuit
50. The purpose of vane relays 1 & 2 provided in the RMPU AC system is to
a) Not to switch ON condenser motors in case of blower failure
b) Not to switch ON compressor motors in case of blower failure
c) Not to switch ON heaters in case of blower failure
d) Not to switch ON entire AC system in case of blower failure
51. The cut in pressure of the reciprocating compressor type WRA used in RMPU coach is
a) 0.3kg/sq cm
b) 0.75 kg/sq cm
c) 1.7 kg/sq cm
d) None
52. The cut out pressure of the reciprocating compressor type WRA used in RMPU coach is
a) 0.3kg/sq cm
b) 0.75 kg/sq cm
c) 1.7 kg/sq cm
d) None
53. In RMPU Ac coaches, the type of expansion valve used is
a) Capillary tube
b) Thermostatic expansion valve
c) Constant pressure expansion valve
d) None
54. In under slung AC coaches, the type of expansion valve used is
a) Capillary tube
b) Thermostatic expansion valve
c) Constant pressure expansion valve
d) None
55. The recommended refrigerant in place of R 12 is
a) R22
b) R134a
c) R100
d) None
56. The type of cables to be provided in new air conditioned coaches
a) Elastomeric copper cables
b) PVC copper cables
c) E-Beam irradiated thin walled elastomeric cables
d) None
57. To avoid fires in AC coaches the minimum clearance between live part and coach body should be a) 4mm
b) 2mm
c) 3mm
d) None
58. To avoid fires in the AC coaches, tape should only be used is
a) The insulating fire retardant low tension (FRLT)
b) PVC
c) Cotton tape
d) All the above
59. Capacity of battery used in RMPU AC coach other than first class is
a) 800AH
b) 1100AH
c) 540AH
d) None
60. Capacity of battery charger used in RMPU AC coach is
a) 200/250 A
b) 40A
c) 70A
d) None
61. Number of lead acid cells available in battery of SG RMPU AC coach
a) 56
b) 54
c) 112
d) None
62. The capacity of HRC fuses to be provided for 1100AH battery of SG RMPU AC coach is
a) 400A
b) 250A
c) 100A
d) None
63. The capacity of plant selector rotary switch RSW2 provided in power panel of RMPU AC coach is
a) 300A
b) 400A
c) 63A
d) None
64. The capacity of HRC fuses both positive and negative to be provided for plant selector circuit in power panel of RMPU AC coach is
a) 400 A
b) 250 A
c) 63 A
d) None
65. The capacity of power selector4 rotary switch RSW1 provided in power panel of RMPU AC coach is
a) 500 A
b) 160 A
c) 16 A
d) None
66. Refrigerant used in under slung AC unit is
a) R22
b) R134a
c) R407C
d) None
67. Compressor system design of under slung AC unit is
a) Open
b) Hermitically sealed
c) Semi sealed
d) None
68. Capacity control of AC under slung unit is about
a) 25% to 100%
b) 50% to 100%
c) 75% to 100%
d) None
69. The system of voltage of under slung AC coaches are
a) 110/135 DC
b) 415V AC
c) 750V AC
d) None
70. The capacity of battery is provided in AC under slung coaches single set of
a) 525 AH 56 cells
b) 800 AH 56 cells
c) 1100 AH 56 cells
d) None
71. The capacity of first class under slung AC system is
a) 5.2 TR
b) 6.7 TR
c) 7TR
d) None
72. Capacity of condenser motor used in first class under slung air condition system
a) 1.0 KW
b) 0.75 KW
c) 2 KW
d) None
73. The capacity of evaporator fan motor used in first class under slung AC coach
a) 1 KW
b) 0.65 KW
c) 1.5 KW
d) None
74. The speed of the condenser fan motor used in AC first class under slung AC coach
a) 1500 RPM
b) 2800 RPM
c) 750 RPM
d) None
75. The speed of the evaporator fan motor used in AC under slung system
a) 1500 RPM
b) 3000 RPM
c) 700 RPM
d) None
76. The total capacity of AC system used in AC two tier and AC composite coach
a) 10.4 tons
b) 13.4 tons
c) 14 tones
d) None
77. The capacity of alternator used in under slung AC chair car, AC sleeper coach, AC composite coach are
a) 18 KW 135V
b) 12 KW 135 V
c) 25 KW 135V
d) 22.5 KW 135V
78. When under slung AC coach is working in normal condition the section pressure gauge reading should be
a) 37-40 PSI
b) 150 to 170 PSI
c) 135 to 150 PSI
d) None
79. When under slung AC coach is working in normal condition the delivery pressure gauge reading should be
a) 37-40 PSI
b) 150 to 170 PSI
c) 50 to 70 PSI
d) None
80. The oil pressure of the compressor is
a) 70 to 90 PSI
b) 150 PSI
c) 200 PSI
d) None
81. Recommended setting of low pressure cut out of under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI
d) None
82. Recommended setting of low pressure cut out of under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI
d) None
83. Recommended setting of high pressure cut out of under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI
d) None
84. Recommended setting of oil pressure cut out for ACCEL and CARRIER in under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI above section pressure
d) None
85. The purpose of low voltage relay (LVR) used in control panel of under slung AC coach is
a) Stop the compressor motor/condenser motor, heaters if the battery voltage less than 100V
b) It cuts of the supply to control circuit
c) It will reset if the battery voltage rises to 102 V
d) All of the above
86. In under slung AC coach, the rating of fuseF2 + provided for protection of heater
a) 125A
b) 63A
c) 10A
d) 2A
87. Recommended grades of oil for compressor are
a) Frezol 3
b) Sheftal 68
c) Servo FreeZ-71
d) Servo FreeZ-66
e) All of the above
88. Chemical name of refrigerant R 134a
a) Dichloro difluoro methane
b) Chloro difluoro methane
c) Tetra fluoro ethane
d) None
89. Size of carbon brushes used in compressor motor of under slung AC in
a) 44.3 x 25.75 x 939 mm x 2
b) 44.5 x 25.4 x 9.52 mm x 2
c) 40 x 32 x 16 mm
d) All the above
90. Size of carbon brushes used in condenser motor of under slung AC in
a) 32 x 20 x 10 mm
b) 32 x 20 x 8 mm
c) 32 x 8 x 10 mm
d) All the above
91. Size of carbon brushes used in condenser motor of under slung AC in
a) 32 x 20 x 8 mm
b) 32 x 22 x 8 mm
c) Both a & b
d) None
92. An electrolyte use in train lighting cell is the mixture of
a) Sulphuric acid and tap water
b) Sulphuric acid and mineral water
c) Sulphuric acid and demineralized/distilled water
d) None of the above
93. When cell is fully charged, the positive plate becomes
a) Lead peroxide
b) Spongy lead
c) Lead sulphate
d) None
94. When the lead acid cell is fully charged the negative plate becomes
a) Lead peroxide
b) Spongy lead
c) Lead sulphate
d) None
95. The capacity of cell is measured in
a) Ampere hour
b) Watt hour
c) Amperes
d) Watts
96. Internal resistance of lead acid cell is mainly due to
a) Size of plates
b) Distance between the plates
c) Nature of electrolyte
d) All the above
97. Trickle charging of storage battery help to
a) Compensate for internal losses
b) Maintains proper electrolyte
c) Increase its capacity
d) None
98. The capacity of Battery used in 110V T.L system
a) 120AH
b) 210Ah
c) 320Ah d) 90AH
99. SPGR of fully charged cell
a) 1.220
b) 1.180
c) 1.140
d) 1.100
100. SPGR of half charged cell
a) 1.210
b) 1.175
c) 1.100
d) 1.140
101. SPGR of fully discharged cell is
a) 1.210
b) 1.175
c) 1.200
d) 1.140
102.Total number of cells available in TL Battery of 110V system
a) 54
b) 56
c) 24
d) 18
103. Sulphation occurs due to
a) Cells kept under discharged condition
b) Cells kept under not fully charged condition
c) Cells over charged
d) All the above
104. The codal life of lead acid TL/AC cells is
a) 4
b) 3
c) 2
d) None
105. The capacity of batteries used for RMPU AC coaches is
a) 525 AH
b) 400 AH
c) 800 AH
d) 1100 AH
106. VRLA Batteries works on
a) Oxygen recombination principle
b) Hydrogen recombination principle
c) Hydrogen-oxygen recombination principle
d) None of the above
107. Normally the VRLA cells mounted in a position.
a) Horizontal
b) Vertical
c) Slanting
d) None
108. VRLA battery separators can be of
a) The gelled electrolyte type
b) The absorbed electrolyte type
c) A & b d) None of the above
109. Conductivity is the ability of a solution to conduct electrical current commonly expressed in
a) Amperes
b) Watt
c) Micro mhos/cm
d) None
110. Conductivity of DM water is measured by
a) Conductivity meter
b) Universal solution
c) pH meter
d) all of the above
111. Acceptable quality of treated water conductivity is in micro mhos/cm
a) <10
b) <30
c) 40
d) None
112. Acceptable quality of treated water PH value will be
a) 6.8 to 7.2
b) 7.5 to 8.5
c) 8.5 to 10
d) None
113. Inverters convert
a) AC into DC
b) DC into AC
c) Both a & b
d) None
114. In 25 KVA inverter the 3 phase AC supply is achieved by boosting DC voltage 100/140 volts into
a) 230V DC
b) 650V DC
c) 415V DC
d) None
115.Out put PWM voltage of inverter section of 25 KVA inverter of RMPU AC coach is
a) 650VDC
b) 220VDC
c) 24V DC
d) 3 phase 415 V AC
116.Alternator is a device that converts
a. Mechanical energy into electrical energy
b. Electrical energy into mechanical energy
c. Chemical energy into electrical energy
d. None of the above
117. Both field winding and 3 phase winding of AC coach alternator 120V are provided on _________
a. Stator
b. Rotor
c. Both a and b
d. None
118.TL/AC coach alternator 120V designed to have ______________
a. Residual magnetism
b. Permanent magnetism
c. Both a and b None of the above
119.Recommended Cut in speed of 4.5 KW TL alternator is by RDSO with MA RR unit ___________
a. 357 rpm
b. 600 rpm
c. 1100 rpm
d. 2500 rpm
120.Minimum speed for full output of 4.5 KW 120V TL alternator, recommended by RDSO is _______
a. 357 rpm
b. 600 rpm
c. 1500 rpm
d. 2500 rpm
121.Maximum speed of TL/AC coach alternator is
a. 400 rpm
b. 800 rpm
c. 1500 rpm
d. 2500 rpm
122.Field coils of 120V TL/AC coach alternator are connected in
a. Series
b. Parallel
c. Star
d. Delta
123.Three phase windings of 120V TL/AC coach alternator are connected in
a. Star
b. Delta
c. Series
d. Parallel
124.Size of V belts used for driving 110V, 4.5KW TL alternators
a. C122
b. C118
c. C124
d. None
125.Size of V belt used for driving 110V, 18, 22.5KW AC coach Alternators
a. C122
b. C118
c. C124
d. None
126.Number of V belts used for driving 110V, 4.5KW TL alternator is ___________
a. 4
b. 6
c. 12
d. None
127.Number of V belts used for driving 110V, 18, 22.5, 25KW AC alternator is ___________
a. 4
b. 6
c. 12
d. None
128.DC output voltage of Alternator /Regulator of 110V, TL/AC coach is
a. (110-140) DC
b. (70-90) DC
c. (90-120) DC
d. None
129.Rated DC output current of 4.5KW 110V, Alternator is ____________
a. 37.5A
b. 19A
c. 43A
d. None
130. Rated DC output current of 18KW 110V Alternator is ____________
a. 193A
b. 175A
c. 135A
d. None
131. Rated DC output current of 25KW 110V Alternator is ____________
a. 193A
b. 175A
c. 135A
d. None
132. Pitch circle diameter of Axle pulley of 110V TL system
a. 200mm
b. 140mm
c. 5726mm
d. None
133.Pitch circle diameter of Axle pulley of 110V AC coach system
a. 200mm
b. 584mm
c. 572.6mm
d. None
134.As per the latest SMI, the voltage setting of alternator 4.5KW 110V for passenger train with flooded batteries is ____________
a. 127V DC b. 124V DC
c. 122V DC d. None 135.As per the latest SMI, the voltage setting of ac alternator 18KW 110V with flooded batteries is
a. 129V DC
b. 124V DC
c. 122V DC
d. None
136.As per the latest SMI, the voltage setting of alternator 4.5KW 110V for passenger train with VRLA batteries is ____________
a. 123+/-0.5V DC
b. 124+/-0.5V DC
c. 121+/-0.5V DC
d. None
137.As per the latest SMI _____the voltage setting of alternator 4.5KW 110V for mail/express trains with VRLA batteries is ____________
a. 123+/-0.5V DC
b. 124+/-0.5V DC
c. 121+/-0.5V DC
d. None
138.As per the latest SMI the voltage setting of alternator 4.5KW 110V for super fast trains with VRLA batteries is ____________
a. 123+/-0.5V DC
b. 124+/-0.5V DC
c. 121+/-0.5V DC
d. None
139.As per the latest SMI the voltage setting of AC coach alternator 110V for passenger train with VRLA batteries is ____________
a. 128+/-0.5V DC
b. 127+/-0.5V DC
c. 126+/-0.5V DC
d. None
140.As per the latest SMI the voltage setting of AC coach alternator 110V for Mail/express train with VRLA batteries is ____________
a. 128+/-0.5V DC
b. 127+/-0.5V DC
c. 126+/-0.5V DC
d. None
141.As per the latest SMI the voltage setting of AC coach alternator 110V for super fast train with VRLA batteries is ____________
a. 128+/-0.5V DC
b. 127+/-0.5V DC
c. 126+/-0.5V DC
d. None
142.The purpose of TL Alternator used in Railways.
a. Charging the coach battery on train run
b. Working of lights and fans in the coach during train run
c. Sharing the load to other coaches in case of emergency
d. All the three above
143.The capacity of alternator used for BG coach 110V Train Lighting system.
a. 3KW
b. 4.5KW
c. 12KW
d. None
144.The capacity of alternator used for BG coach 110V roof mounted AC coach
a. 12KW
b. 18KW
c. 25KW
d. None
145.The capacity of alternator used for BG coach 110V under slung AC coach.
a. 25KW
b. 12KW
c. 18KW
d. None
146.The PCD (pitch circle diameter) of 25KW 110V alternator pulleys is
a. 584mm +/- 0.4mm
b. 200+/-0.3
c. 140 mm
d. 100 mm
e. None
147.The field resistance of 4.5KW 110V TL alternator has
a. 4.5 +/-0.5 ohms
b. 6.0+/-0.5 ohms
c. 10+/-0.5 ohms
d. None
148.The resistance between two phases of 4.5KW 110V TL alternator is
a. 0.4 +/-0.05 ohms
b. 0.8 +/-0.10 ohms
c. 4.5 +/-0.5 ohms
d. None
149.The purpose of providing anti rotating clamp near suspension arrangement of alternator is
a. Not to rotate suspension pin of alternator
b. Not to damage the nylon bushes of alternator/ suspension bracket
c. Not to damage the suspension bracket/boss of alternator
d. All of the above
150.The insulation material recommended for alternator windings of 3&4.5 KW 110V shall be __________ class.
a. A
b. B
c. F
d. None
151.The voltage setting of Alt/RR unit is to be set in far with current and RPM for 4.5KW is
a. Half rated capacity of the alt as load as 1500 RPM
b. ¼ rated capacity of the alt as load at 1000 RPM
c. Full rated capacity of alt as load at 2550 RPM
152.While measuring insulation resistance of 110V alternator/rectifier cum regulator the rating of megger is to be used is
a. 100V DC megger
b. 500V DC megger
c. Both a and b
d. None
153.The resistance between two phase of 25KW KEL alternator is about
a. 0.0530746 ohms
b. 0.034 to 0.038
c. 44.2 mille ohms
d. None
154.The field resistance of 25KW KEL alternator about
a. 9.7568 ohms
b. 8+/-0.5 ohms
c. 10.72 ohms
d. None
155.The gap between two halves of axle pulley to be maintained is
a. 3.0 +/-0.5 mm
b. 6mm +/- 0.5 mm
c. 4mm +/- 0.5 mm
d. None
156.Codal life of 4.5, 18, 22.75 & 25 KW alternator / RR unit
a. 12 years
b. 25 years
c. 15 years
d. None
157.Codal life of 120 AH VRLA Battery
a. 5 years
b. 4 years
c. 3 years
d. None
158.Codal life of 120 AH Flooded Battery
a. 5 years
b. 4 years
c. 3 years
d. None
159.Codal life of Battery charger
a. 12 years
b. 15 years
c. 25 years
d. None
160.Codal life of Coach wiring
a. 12 years
b. 15 years
c. 20 years
d. None
161.Codal life of Carriage fans
a. 10 years
b. 12 years
c. 15 years
d. None
162.The distance to be maintained while fixing axle pulley on wheel, from wheel hub to axle pulley outer wedge for 25 KW alternator is
a. 225 mm
b. 240 mm
c. 145 mm
d. None
163.The distance to be maintained while fixing axle pulley on wheel, from wheel hub to axle pulley outer wedge for 18 KW alternator is
a. 225 mm
b. 240 mm
c. 145 mm
d. None
164.The distance to be maintained while fixing axle pulley on wheel, from wheel hub to axle pulley outer wedge for 4.5 KW alternator is
a. 225 mm
b. 240 mm
c. 145 mm
d. None
165.‘V’ belt dropping/smoking/burning due to mechanical failure
a. Brake block jamming
b. Guide cups of damper’s have dropped
c. Both a and b d. None
166.‘V’ belt dropping/smoking/burning due to electrical failure
a. Load on Alt is heavy
b. Wrong alignment
c. Loose/excessive tension
d. All of the above
167.The minimum insulation resistance to be maintained for 4.5KW alternator is
a. 1 Mega ohm
b. 2 Mega ohm
c. 20 Mega ohm
d. None
168.The minimum insulation resistance to be maintained for 18, 22.75 & 25 KW alternators
a. 20 mega ohm
b. 2 Mega ohm
c. 5 Mega ohm
d. None
169.No. of ET’s used in 25 KW RR Unit MA type
a. 2
b. 1
c. Zero
d. None
170.No. of MA’s used in 25 KW MA type RR Unit
a. 2
b. 1
c. Zero
d. None
171.Width of grooved axle pulley of 4.5KW alternator is
a. 200mm
b. 190mm
c. 136mm
d. None
172.Width of grooved axle pulley of 18, 22.5, 25 KW alternator is
a. 200 mm
b. 190 mm
c. 136 mm
d. None
173.The type of suspension bushes are to be provided TL/AC alternators/ suspension bracket as per RDSO specification no RDSO / PE/Ac/0006/99 (Rev.0)
a. Cast nylon bushes
b. Nylon 66 bushes
c. MS bushes
d. All of the above
174.Residual magnetism lost in the alternator core the reason is
a. Field polarity changed
b. Alternator is in idle condition for long time
c. Both a and b
175.As per the Railway Board letter No. 2006/Elec(G)/138/3Pt. I unit Exchange spare recommended for alternators and Regulators for TL/AC depot
a. 5%
b. 10%
c. 15%
d. None
176 .ERRU stands for
a. Electronic Rectifier cum Regulator Unit
b. Electro magnetic Rectifier cum Regulator unit
c. Electrostatic Rectifier cum Regulator Unit
d. None
177. IGBT stands for
a. Insulated Gate By polar Transistor
b. Injection Gate By polar Transistor
c. Indicator gate By polar Transistor
d. None
178. IGBT is
a. Fast switching device
b. Slow switching device
c. Very fast switching device
d. None
179. The size of capacity of fuses to be provided for 25kW ERRU in phase circuit
a. 160A
b. 200A
c. 220A
d. None
180.UVC used in ERRU must be
a) Suitable to work with all capacities
b) Suitable to work with all makes
c) Both a and b
d) None
181.The battery charging current limit with 4.5kW ERRU is to be set at
a. 24A +/-2A
b. 12A +/- 2A
c. 36A +/- 2A
d. None
182.The battery charging current limit with 25kW ERRU when both alternators are paralleled is to be set at
a. 110A +/-5A
b. 220A +/- 5A
c. 220A +/- 10A
d. None
183.The battery charging current limit with 18kW ERRU when both alternators are paralleled is to be set at
a. 80A
b. 160A
c. 240A
d. None
184.OVP provided with ERRU, shall latch before output voltage reaches to
a. Surge voltage
b. Over voltage
c. Both a and b
d. None
185.The rating of field fuse provided in HMTD ERRU
a. 10A
b. 20A
c. 15A
d. None
186. Matched set of ‘V’ Belts means
a) One belt drive
b) More than one belt drive length with in specified limits
c) More than one belt drive length not in specified limits
d) None of the above
187. Number of V Belts required for SG non AC coach of TL alternator
a) 3
b) 4
c) 2
d) None
188. The cross section of V belt is shaped roughly like
a) Isosceles Trapezium
b) Rectangle
c) Square
d) None
189.The gauge used for checking groove angle of axle and alternator pulley is a) No go & go gauge b) Pitch length gauge
c) Section gauge
d) None
190.The gauge used for checking pitch length of V belt is
a) No go & go gauge
b) Pitch length gauge
c) Section gauge
d) None
191. Capacity of Alternator of Train lighting 110V DC BG coach
a) 3KW
b) 4.5KW
c) 25KW
d) 18KW
192.3 phase Bridge rectifier in R.R. box converts
a) AC to DC
b) DC to AC
c) Pulsating AC
d) None
193. Regulator controls
a) Field voltages
b) Field currents
c) DC output voltage
d) DC output current
e) All the above
194.Capacity of Phase fuse provided in 4.5kW R.R.Box
a) 35A HRC
b) 16A HRC
c) 6A HRC
d) 10A HRC
195.Capacity of Field fuse provided in the 4.5kW Rectifier cum Regulator box
a) 35A HRC
b) 6A HRC
c) 16 HRC
d) 10A HRC
196.Capacity of HRC fuse provided for negative circuit in Rotary junction box excluding alarm chain pulling indication light circuit.
a) 35A HRC
b) 16A HRC
c) 6A HRC
d) 10A HRC
197.Capacity of HRC fuses provided for positive circuit in RJB excluding alarm chain pulling indication light circuit.
a) 16A HRC
b) 35A HRC
c) 10A HRC
d) 6A HRC
198.Capacity of Limit switch provided for Alarm chain pulling indication light circuit is
a) 10A
b) 15A
c) 35A
d) 40A
199.Positive and Negative cables in roof run through on either side of coach to avoid.
a) Earth leakages
b) Over loads
c) Short circuits
d) None
200.Level of Illumination is measured by
a) Multimeter
b) Techno meter
c) Lux meter
d) Conductivity meter
201.Recommended level of minimum illumination to be attined in Second class compartment with F.T Fittings.
a) 30Lux
b) 40Lux
c) 16Lux
d) 60Lux
202. Recommended size of Aluminium cables for B +ve and B –ve in 110V coaches.
a) 16sqmm
b) 35sqmm
c) 4sqmm
d) 50sqmm
203.The wattage of TL Fan
a) 32W
b) 10W
c) 80W
d) 60W
204.The capacity of battery fuse for 110Volt SG TL coach is
a) 40A HRC
b) 16A HRC
c) 10A HRC
d) 4A HRC
205.The minimum clearance between the top of the battery and battery box for maintenance of cells shall have
a) 50mm
b) 150mm
c) 100mm
d) None
206.M.S.Rod/MS Flat provided in the battery boxes after loading cells. The purpose of M.S Rod/MS FLAT is
a) Anti theft arrangement
b) To strengthen the battery box
c) Not to drop batteries on run
d) All the above
207.Total number of mono block batteries for one set of 110V TL coach are .
a) 9
b) 12
c) 18
d) 54
208.The voltage of mono block battery of 110V coach is
a) 2V
b) 1.5V
c) 6V
d) 1V
209.Total voltage of one battery set (18 mono blocks or 54 cells) of 110V TL coach.
a) 24V
b) 108V
c) 120V
d) 110V
210.The insulation resistance of 110V coach when measured with 500V Megger during healthy weather condition.
a) 2 mega ohms
b) 1 mega ohms
c) 3 mega ohms
d) 0.5 mega ohms
211.The insulation resistance of 110V coach when measured with 500V Megger during adverse weather condition.
a) 2 mega ohms
b) 1 mega ohms
c) 3 mega ohms
d) None
212.Capacity of Rotary switches provided in Rotary junction box is
a) 40A
b) 16A
c) 10A
d) 15A
213. 204. NName of the meter used to measure Air velocity ( B )
a. Multi meter c. Thermometer
b. Anemometer d. Ammeter
214. Rating of Static inverter used in SG AC Coaches ( C)
a. 20 KVA c. 25 KVA
b. 35 KVA d. 22.75 VA
215. In regulator how many windings are available in Magnetic amplifier ( A&C)
a. 6 c. 4
b. 3 d. 5
216. Size of V belts used for 25KW Alternator ( C )
a. C121 c. C122
b. C123 d. C124
217. Name the meter used to measure relative humidity ( A)
a. PSYCROS meter c. Humidity meter
b. Multi meter d. Voltmeter
218. 1 ton of refrigeration is ( D )
a. 12 BTU c. 1200BTU
b. 120 BTU d. 12000 BTU
219. Thermostat Setting for WINTER used in AC coaches ( C )
A 19, 19, 21 c. 17, 19, 21
b. 22, 22, 24 d. 20, 21, 22
220. Calculate degree of Fahrenheit equivalent to – 40°C ( C )
a. 40°F c. – 40°F
b. – 20°F d. – 50°F
221. The gap between the two halves of axle pulley should be ( B )
a. 0.5 – 1.0 mm c. 3.0 – 4.0 mm
b. 2.0 – 3.0 mm d. 5.0 – 5.5 mm
222. Required level Torque Newton/meter to tightened the nuts and bolts OF Amar Raja cells (VRLA) connection ( C )
a. 10 c. 11
b. 12 d. 13
223. What are the AH capacity of cells used in AC coaches ( A )
a. 800, 1100 c. 120, 800
b. 500, 120 d. 120, 240
224. State the standing pressure of F – 12 refrigerant used for in AC coaches ( B )
a. 60 to 70 c. 70 to 80
b. 80 to 90 d. 50 to 60
225. Name of the Acid used in lead acid cells ( A )
a. Sulphuric Acid c. Nitric acid
b. Hydrochloric Acid d. Phosphoric Acid
226. Give the Spg & Voltage of Fully charged cells ( A)
a. 1220 & 2.2 c. 1200 & 2.2
b. 1220 & 2.1 d. 1200 & 2.1
227. Cut in speed for B/L alternator for 25KW Alternator ( D )
a. 17 KMPH c. 20KMPH
b. 19 KMPH d. 22 KMPH
228. Inverter converts ( A )
a. DC to AC c. AC to AC
b. DC to DC d. AC to DC
229. Function of SPP relay ( A )
a. Preventing single phasing c. Preventing shorting of phases
b. Both d. None
230. Function of proving relay ( B )
a. Ensure of starting of heater /compressor before blower c. Ensure of starting of compressor before blower
b. Ensure of starting of blower motor before compressor/heater d. Ensure of starting of liquid receiver.
231. Cooling thermostats setting (mercury thermostats) in I AC coach ( A )
a. 22, 24, 26 c. 17, 19, 21
b. 24, 24, 26 d. 19, 19, 21
232. IGBT are used as ( A )
a. High frequency switching device c. Low frequency switching device
b. Illuminating device d. Amplifier
233. Battery fuse rating in AC coaches is ( A )
a. 250 A c. 600 A
b. 400 A d. 200 A
234. No of regulators are available in I AC coaches ( A ) a. 1 c. 2 b. 3 d. 4
235. One RMPU AC coach is provided with how many compressors. ( A )
a. 4 No’s sealed compressor c. 4 No’s open type compressor
b. 2 No’s sealed compressor d. 2 No’s open type compressor
236. PSI is the unit of ( A )
a. Pressure c. Humidity
b. Temperature d. Velocity of gas
237. Boost charge of VRLA cells ( A)
a. 2.3 V/Cell c. 2.25 V/Cell
b. 110 V/Cell d. 115 V/Cell
238. Trickle charging of VRLA cell ( C )
a. 2.3 V/Cell c. 2.25 V/Cell
b. 110 V/Cell d. 115 V/Cell
239. No of MA’s in 25 KW regulators ( C )
a. 1 c. 2
b. 3 d. 4
240. No of ET’s in 25 KW regulators ( A )
a. 1 c. 2 b. 3 d. 4
241. Rectifier converts ( B )
a. DC to AC c. AC to AC
b. AC to DC d. DC to DC
242. HP cut out trips the compressor in Under Slung AC Coaches ( A )
a. 17.6 Kg/cm² c. 0.76 Kg/cm²
b. 7.6 Kg/cm² d. 76 Kg/cm²
243. LP cut out trips the compressor in Under Slung AC Coaches ( C )
a. 17.6 Kg/cm² c. 0.76 Kg/cm²
b. 7.6 Kg/cm² d. 76 Kg/cm²
244. Heater coil rating in I AC coaches is ( A )
a. 3 KW c. 4 KW
b. 5 KW d. 7 KW
245. Give the half load setting of R/R of 25 KW AC ( A)
a 95 c. 100
b 90 d. 85
246. Named the meter used to measure Vacuum ( A )
aMicron c. Picron
bTrivector d. Sicron
247. Give the diameter of Axle pulley used in AC coaches ( B )
a546.6 mm c. 500.6 mm
b572.6 mm d. 600.6 mm
248. Give the tension length of spring used in Tension rod of 25 KW Alternator ( A )
a 260 mm c. 269 mm
b 265 mm d. 275 mm
249. Why lead acid cells are called as Secondary cells ( C )
a Since it can’t be recharge c. Since it can be recharge
b Since it can’t charge initially d. None
250. What is Pre cooling ( A )
a Cooling of AC coach before placing on PF c. Cooling of AC coach while running
b Cooling of AC coach after starting the train d. None
251. Give the DC link voltage in static inverter ( B )
a 500 c. 400
b 600 d. 700
Write down the abbreviation.
1 PWM PULSE WIDTH MODULATED
2 VRLA VALVE REGULATED LEAD ACID
3 IGBT INSULATED GATE BIPOLAR TRANSISTOR
4 FRPCPY FAILURE RATE PERCENTAGE PER YEAR
5 BTU BRITISH THERMAL
UNIT II.
True of False
01. Expansion valve expands the gas irrespective of load (T / F) FALSE
02. M – 22 gas is used in RMPU’S (T / F) TRUE
03. Refrigerant requirement in U/S AC plant is approximate 27 Kg (T / F) FALSE
04. Refrigerant requirement in RMPU AC plant is approximate 15 Kg (T / F) FALSE
05. Vane relay ensured that blower motor has started before switching on compressor. (T / F) TRUE 06. TDR setting between 2 compressor of one RMPU is 10 Sec (T / F) FALSE
07. One coach (RMPU) is having 4 No’s of inverters (T / F) FALSE
08. BCK compressors are sealed compressor (T / F) TRUE
09. Manu rope compressors are sealed compressor (T / F) TRUE
10. ACCEL compressors are sealed compressor (T / F) FALSE
252. Function of cooling pilot relay ( A )
a Ensure the function of Compressor c. Ensure the function of heater
b Ensure the function of Compressor/Heater d. None of the above 65
OBJECTIVE TYPE.
1. The process of removing heat from low temperature level and rejecting at high temperature is called. REFRIGERATION
2. Any substances for change of its state at constant temperature absorbs/give up heat is called. LATENT HEAT
3. The sum of sensible heat and latent heat of substance in process is called ENTHALPY.
4 The latent heat of fusing ice is 144 BTU/LB
5. The unit of refrigeration is TON OF REFREGIRATION – 12000 Btu/Hr or 3023.98 K.Cal/Hr
6. The temperature measured by ordinary thermometer is called SENSIBLE HEAT of the temperature.
7. What is the boiling point of water 100 ◦C
8. AT what temperature water starts freezing_ 0 ◦C
9. One watt is 3.412 BTU.
10. One BTU is 0.252 K.calaries.
11. The unit of heat is BTU OR K.CAL
12. RMPU means ROOF MOUNTED PACKAGE UNIT
13. The setting of HP cutout in RMPU coaches is 415 psi
14. The setting of LP cutout in under slung coaches is 35 psi
15. The boiling point of refrigerant R22_ -40.8 ◦C
16. The boiling point of refrigerant R12. – 29.8 ◦C
17. Freezing point of refrigerant R22
18. R12 is being replace with R-134A in latest Refrigeration system.
19. The latent heat of evaporation IS THE HEAT REQUIRED TO CHANGE THE LIQUID INTO VAPOUR.
20. The temperature maintained in the refrigerator is LESS then 0 degree C.
21. The dry bulb and vet bulb temperatures equals then the RH is 100%
22. The moisture absorption in refrigeration circuit is done by DEHYDRATOR CUM FILTER
23. The commonly used refrigerants are R 12 & R 22
24. The lubrication of system in the sealed compressors is done by FREEZOL
QUESTION BANK FOR ELECTRICAL POWER MAINTENANCE
1. Layout of sub-station, maintenance
2. Transformer and its maintenance
3. Circuit breakers
4. House wiring and techniques
5. Underground cables
6. Motors
7. D.G sets
8. Pumps
9. Tariffs, power factor
10. Insulating materials 1
11. Regulations for power line crossings
TRANSFORMERS
1. What is the transformation ratio?
E2 = N2 = I1 E1 N1 I2 Where,
E2 = secondary voltage
E1 = primary voltage
N2 = no. Of secondary turns
N1 = no. Of primary turns
I2 = secondary current I
1 = primary current.
2. What is the E.M.F. equation of a transformer?
E1 = 4.44φmax fN1 volts
E2 = 4.44φmax fN1 volts Where,
φmax = maximum flux,
webers F = frequency, hertz
3. What are the fittings and accessories should be provided on a transformer?
The fittings and accessories of a transformer are:
1) Thermometer.
2) Silicagel breather.
3) Bottom valve.
4) Top valve.
5) HT and LT bushings.
6) Terminal Box.
7) Bucholz relay.
8) Conservator.
9) Tap changer.
10) Inspection covers.
11) Rating plate.
12) Oil and temperature indicator.
4. What is an auto transformer and what is its main advantage?
An auto transformer can be conceived of as conventional transformer with two windings, but secondary winding is connected in series with the primary windings. An auto transformer is smaller in size, lower cost, lower losses and high efficiency since the rating of the transformer is less than that of conventional two winding transformer for the same rated output.
5. What are the essential conditions for parallel operation of transformer?
a) They should have same polarity.
b) They should have same voltage ratio.
c) They should be of same percentage impedance.
d) They should be of same phase rotation for three phase transformers.
e) They should have identical vector diagram and phase displacement for three phase transformers.
6. What are the two basic types of instrument transformers?
They are
1. Current transformers.
2. Potential transformer. The secondary rating of Potential transformer is 110 volts and that for current transformer is 5 amperes, occasionally 100 volts and 1 ampere for PT and CT respectively may be available.
7. Why are transformers fitted with oil conservator?
The provision of conservator is to ensure that the transformer is completely filled with oil at all times, and to provide for the expansion and contraction of the oil due to temperature variations in the windings and minimum oil surface is exposed to the air.
8. What is the function of the breather?
Breather is provided on the transformer to prevent contamination of the transformer oil in the conservator, by the moisture present in the air entering the conservator. Generally breather is packed with silica gel crystals which has the property of absorbing all water vapour contained in the air passing through it, thereby making the air dry.
9. What is the function of a circuit breaker?
It has two functions:-
1) Protective function: During faulty/abnormal conditions without flash.
2) Controlling function: During normal conditions i,e, switching ON/OFF loads etc,. In oil circuit breakers, oil is the media to extinguish the arc developed during the operation of contacts and used for higher rating circuits.
10. What is the impedance voltage of transformer?
When impedance voltage is applied across one winding of a transformer it produces normal full load current to flow through secondary winding when its terminals are short circuited. It is 10% of the rated voltage and expressed as percentage of the applied voltage.
11. What is the efficiency of the transformer?
The efficiency of transformer is given by output divided by the input. = Output in watts X 100 / output in watts + Total losses in watts. The efficiency will be highest at a percentage load = 100 X square root of Iron loss / Copper loss.
12. Explain the regulation of transformer?
Regulation of transformer refers to the percentage voltage drop from no load to full load at unity power factor. In the larger sizes of transformers, the percentage regulation is of the order of 2 to 4 percent.
13. Briefly explain the maintenance schedule to be carried out on a transformer?
1. Hourly:
a. Load in Amps: Check against Rated figure and balance the load in 3 phases.
b. Voltage: Check against rated figure.
c. Temperature: Oil Temp and ambient Temp.
2. Daily:
a. Silica Gel: Check condition of silica gel and recondition / replace if required.
3. Monthly:
a. Conservation tank: check oil level and top up if necessary.
b. Humming sound: Check for abnormal humming of Transformer and attend.
c. Oil leakages: Check and attend the leakage on transformer body, conservator tank, oil drain valve radiators.
d. Tap changer switch: check for free movement of tap changer switch. Tap position to be clearly seen.
e. Connections: Check tightness. If loose tighten.
4. Quarterly:
a. Bushings: Check condition of bushings, clean the bushings.
5. Half yearly:
a. Non conservator transformer: check for moisture under cover and improve ventilation.
b. Cable boxes: check cable boxes (For indoor transformers)
c. Explosion vent diaphragm: check condition of explosion vent diaphragm. d. Gasket joints: check for oil leakage.
6. Yearly: a. Oil in Transformer: Check for
i. Dielectric strength.
ii. Water content
iii. Sludge
iv. Acidity
v. Dissolved gases
b. Earth resistance: Measure the earth resistance.
c. Relays, Alarm their circuits: Check functioning of relays, alarm & their circuit.
7. 2 yearly: Non conservator transformers: Internal inspection above core. Filter oil regardless of condition.
8. 5 yearly: Over all inspection including lifting of core and coils.
14. What is the function of Explosion vent? Explosion vent is provided for transformer this act as a pressure safety valve & burst in case excess pressure is developed in the transformer tank.
15. Explain the term Insulation resistance and the procedure for measurement of the same. Any electrical equipment can be operated at rated voltage / potentials. Hence it should be insulated according to potentials to give safety to the operator, so that potential to be zero on outer surfaces. The insulation resistance of equipment refers to the resistance between live/conducting part of equipment and earth. The insulation resistance can also be measured between two circuits separated by insulation. The IR can be measured by a Megger i.e., one terminal of megger is connected to conducting part and the other to the earth(or conducting circuit separated by insulation) and operate Megger and record the ohmic values on the scale which is from zero to few mega ohms.
16. What are the possible causes for the low insulation resistance, and their remedies?
Due to moisture – Joints should be tightened and in places where silica gel is provided should be replaced with pure blue colour. Due to Low BDV of Oil – New fresh filtered insulating oil with correct BDV is to be replaced. Due to defective Insulation tie rod – Correct insulation tie rod is to be provided. Insulators flash over – Insulators are to be cleaned periodically from dust and other foreign materials and cementation Part Earthing due to tracking. It should be cleaned properly. Due to oil deposits – Oil should be cleaned thoroughly with dry cloth.
17. Briefly explain the working of a diesel engine. The conversion of energy stored in a fuel can be considered in Two steps. In the first step, the fuel is burnt to release heat energy. In the second step, this heat energy is converted to mechanical energy. When the above two actions take place in two separate devices, the heat engine is known as an external combustion engine. Eg. Steam engines. When both actions, of burning fuel and conversion of energy, takes place inside the engine, the engine is known as an Internal combustion engine. Eg. Petrol and diesel engines used in Automobiles and pump sets etc., In such engines, the fuel is burnt within the engine and the resulting heat energy converted into mechanical energy.
18. Discuss the functions of the following system of a diesel engine
A) Fuel Injection system: The function of this system is to draw fuel from the fuel tank, clean it, raise its pressure and supply it in form of a high pressure spray at the proper moment in the cylinders.
B) Cooling System: Only a part of the heat energy of fuel is converted to mechanical energy in an engine. Due to very high temperature, the engine components gets heated. This continuous heating may cause some problems. In order to avoid such problems, the engine cylinders are continuously cooled. There are two types of cooling systems. Viz., Air cooling and water cooling.
C) Starving system: The crank shaft must be turned by some outside means for the first few cycles and after which it continuously runs . The types of starting systems are hand starter, Petrol engine starting, Compressed air motor starting. .
D) Lubricating system: There are many moving parts in an engine such as piston moving In a cylinder, two ends of connecting rod moving round piston and crank pins, crank shaft moving on its bearings etc., In order to reduce friction in these parts, they are to be lubricated. Lubricating oil is stored in the lower part of the engine and a pump delivers the oil to the different components needing lubrication.
19. List out the moving and stationary parts of a diesel engine. Cylinder block, Cylinder liners, Dry liners, Wet liners, Cylinder head, Head gaskets, Exhaust manifold, Crank shaft, Crank case, oil pan, piston, Expansion control,, piston head shoes, Piston rings, Oil control ring, piston pin, Connecting rod, Vibration damper, fly wheel, Main bearings, Valve actuating mechanism, Hydraulic valve lifter, Rocker arm, Cams and Camshaft, gears.
20. Explain the word ignition. Ignition system is to reduce a spark in the petrol engine cylinder, at the end of the compression stroke and to ignite the air fuel mixture.
21. Explain the objectives of lubrication and the parts that needs lubrication. When a body is in motion relative to other bodies, there is a force of friction between them, which opposes the motion and produces heat, resulting in wear of the metal surface. To reduce this friction and wear of the moving parts, Inter posing of some lubricating oil between the two surfaces.
a) Cylinder walls, Piston rings
b) Gudgeon pin (Small end of connecting rod)
c) Crank pin ( Big end of connecting rod)
d) Main crank shaft bearing
e) Timing gears
f) Crank shaft bearings
G) Valve mechanism
22. Discuss the checks to be made during the normal running of the engine
a) Fuel system
b) Lubricating system
c) Cooling system
d) Starting system
e) Exhaust system
f) Leaks of fuel, Water or Lubricating oil
g) Loose fastening
h) Unusual mechanical noise
i) Looseness of belt.
23. What are the maintenance records and how they are useful? What records are to be maintained for a D.G set?
The Maintenance records provide very useful information. By reference to these records, one can anticipate renewal or replacement of the components and can plan their stocking. Also the preventive maintenance schedules can be reviewed on the basis of such records. These records can also reveal weakness in the equipment, which can be corrected. For a D.G set the following records are to be maintained:
a) Cooling water inlet and outlet temperature
b) Exhaust temperature
c) Lubricating oil pressure, temperature
d) Generator voltage, current, frequency etc.,
e) Hours of operation
f) Fuel consumption
g) Lubricating oil consumption
h) KWH generated
i) Results of inspection and measurements on each Inspection.
j) Replacement of parts/components due to failure/wear and tear/breakdown.
24. How diesel engines are rated?
The manufacturers of diesel engines are Supposed to state the break power that their engine can develop at a given speed. This break power at a particular speed is known as its Rating, The break power can be expressed either in terms of Horse power of Kilo watts and speed is expressed in RPM. Max. Rating: It is the Horse power at a particular speed which the engine can develop for a short duration ie., 5 mts—30% Intermittent Rating: It is the Horsepower at a particular speed, which the engine can develop for about one hour---15% Continuous Rating: It is the Horse power at a particular speed which the engine develop with out interruption.
25. Discuss the importance of the preventive maintenance of a diesel engine. Components of an engine take wear and tear during their work. These components need periodical checking/servicing/replacement. To facilitate periodical checking/servicing/replacement of parts, periodical maintenance schedules are made. If such schedules followed strictly, the chances of unexpected maintenances are rare. The schedules as well planned maintenance is known as Preventive maintenance there by avoiding the break down of equipment and work interruption.
26. Explain the cleanliness of the diesel oil. The diesel engine fuel injection pump and fuel injector are having very close tolerance. If the diesel sent to these components is clear and chemically satisfactory, there will be very little wear of these components even after prolonged operating. However it may not be possible to obtain absolutely clean diesel fuel at the refineries. Hard and sharp foreign particles available in the oil cause accelerated wear of fuel injection system components. To minimize such damage due to fuel contamination, extreme care is required during installation of different fuel lines, for which a no. of filters, water separators are permitted.
27. What are the different checks to be carried out on D.G sets. What are the items to be checked in ‘A’. Check and explain the nature of check.
1. Lubricating Oil: Check the lubrication oil level in engine and governor and top up if necessary. Check the oil bath level.
2. Radiator water: Check radiator water level. Check oil bath cleaner oil level.
3. Air cleaner oil: Check the condition of pre-cleaner dust pan. Check the condition of air cleaner restrictions.
4. Fuel System: Check and record fuel oil. Drain sediment from Fuel Tank.
5. Battery: Clean the battery. Tight the connection.
6. Switch gear: Check automatic starting switch for its proper functioning. Clean the D.G Set.
7. D.G Set: Check the condition of belt for its proper tension. Observe Oil leakages. Observe abnormal sound. Record lub oil pressure Record Voltage Record Load Current Record KWH Meter reading.
28. What are the functions of starter? Ans. The functions of starter are:
(i) To start, and stop the motor
(ii) To limit the starting (or inrush) current, when necessary
(iii) To permit automatic speed control, when required, and
(iv) To protect the induction motor as well as the connected equipments from the sustained over-load, no-voltage, under-load, etc. Conditions.
29. How many types of 3-phase motors are there? There are two types of 3-phase motors:
(1) Squirrel cage rotor type
(2) Wound rotor type
30. What are the various starters used? Ans. Direct online starter and Star delta starter for squirrel cage induction motor. Rotor rheostat starter for slip ring induction motor.
31. Draw the internal connections of a DOL starter?
32. How many types of squirrel cage rotor are there?
There are two types of squirrel cage rotors:
(1) Single cage,
(2) Double cage
33. What is the formula for determining the synchronous speed and no. Of poles of an induction motor? Synchronous speed, Ns = 120f R.P.M. P And no. Of poles, P = 120f 75 Ns Where, f= frequency in hertz F=50Hz then: Ns=120 x 50 P =6000 R.P.M. P And P= 6000 Ns
34. Explain in brief the working principle of a 3-phase squirrel cage induction motor. On connecting the stator windings to a 3-phase source of supply, a 3-phase rotating magnetic field is developed in the stator. An e.m.f. is induced in the rotor bars due to which conduction of current is established in the bars which develops a torque and sets the rotor into rotation.
35. Explain in brief the working of a 3-phase slip-ring induction motor. The stator of a slip-ring induction motor is identical to a squirrel-cage induction motor’s stator. The rotor of this type of motor is wound like its stator. The no. Of poles and phases of rotor-windings are the same as of stator-winding. The 3 one side terminals of three rotor-windings are joined at one point to make a star-connection and the other 3 terminals connected to 3 slip-rings. These slip-rings are connected to an external 3-phase rheostat by means of 3 carbonbrushes. The external resistance is added to the rotor winding circuit for increasing the starting torque and decreasing the starting-current at the time of starting the motor as shown in the figure. As the motor attains its normal speed, the external resistance is cut gradually and finally the slip-rings get short-circuited. If the rotor resistors of a slip-ring induction motor are connected in delta then a parallel circuit will be formed. Then the total resistance will be smaller than their individual resistances. Rheostat-resistors connected in delta will not fulfil the condition of producing high starting torque. Therefore, the rheostat-resistors should be connected in star only. Wound-rotors are costlier than squirrel-cage rotors but their starting torque is much higher than that of squirrel-cage rotors.
36. Write the names of various single phase (φ) motors. The names of various single phase motors are follows:
(1) Split-phase (φ) motor,
(2) Capacitor motor (a)capacitor-start motor,(b)capacitor-run motor,(C) capacitor-start capacitor-run motor or double capacitor motor.
(3) Shaded pole motor
(4) Universal motor or A.C. series motor or AC/DC motor
(5) Repulsion motor –
(a) plain repulsion motor,
(b) repulsion-start induction-run motor,
(c) repulsion induction motor.
37. Why are the single phase (φ) induction motors not self-start?
Because of only one phase (φ) winding, there is no rotating magnetic field in a single phase induction motor. Since, the field has no rotating nature, hence, it is incapable to rotate the rotor and the motor can’t start by itself.
38. Draw a connection diagram of a capacitor-start induction motor.
39. Give the names of main parts of a capacitor start motor.
(1) Stator, made by joining together the slotted silicon-steel laminations.
(2)Running winding, which is made of copper wire and is fastened in the slots.
(3) Squirrel cage rotor, made by joining together the silicon-steel laminations.
(4) Centrifugal switch whose operating device is mounted on the shaft and the switch is fitted Inside a Bakelite box.
(5)Electrolytic capacitor fitted to the motor’s body.
(6) Bearings (ball or journal), both end-covers, terminal-plate.
40. What may be the possible causes if a motor starts with a difficulty of supplies a low torque? The possible causes may be as follows:
(1) Defective capacitor,
(2) Worn out bearings,
(3) Short-circuit in the starting or running winding,
(4) Loose rotor-shaft, (5) Wrong connections.
41. What may be the possible causes if a capacitor motor begins to emit smoke on starting?
(1) winding are short-circuited,
(2)Centrifugal switch fails to put ‘OFF’ the running winding,
(3) Bearings are worn out.
42. What are single –phase motors? Motors which operate on single phase supply and are of generally fractional horse power with a reading of less than 1 HP.
43. How would you reverse the direction of a rotation of a capacitor start-inductionrun motors? By reversing either the running or starting-winding leads where they are connected to the line. Both must not be reversed.
44. What is a universal motor? It is built like a series D.C motor with the difference that both the stator and armature are laminated. They can be used either on d.c or a.c.
45. What could be the reason if a split phase motor runs too slow? It could be due to starting winding being open or grounded or burnt out.
46. What are the various Starter used? DOL Starter, Star Delta starter, Rotor rheostat starter.
47. Enumerate the possible reason if a 3-phase motor fails to start? Any one of the following reasons could be responsible:
1. One or more fuses may be blown.
2. Voltage may be too low
3. The starting load may be too heavy
4. Worn bearing. 48. A motor stops after starting i.e. it fails to carry load. What could be the causes? Any one of the following: a. Hot bearing, which increase the lo
ad by excessive friction
b. Excessive tension on belt, which causes the bearing to heat.
c. Single phase on the running position of the starter.
49. What is meant by single phasing and what are it causes? By single phasing is meant the opening of one wire (or leg) of a three phase circuit.
50. What is jogging? It means inching a motor i.e. to make it move a little at a time by constant starting and stopping.
51. What are the maintenance schedule of motors? The following are the maintaining schedules. Occasionally Check motor for over heating. Terminal connection should be tightened, ventilation slot to be cleaned and kept free. Monthly Motors is dusty loactions. Blow out dust from windings. Quarterly Control equipment. Check for proper function. Correct for settings. Belts. Check belt tension. Excessive belt tension to be reduced. Loose belts to be adjusted. Brush holders& brushes of slip ring motors. Check for proper bedding of brushes. Align brush holder replace brushes if necessary. Half yearly Ball/roller bearings. Check foe sufficient grease. Make up grease if necessary. Avoid over greasing. Annual Winding of motors. Check for abrasion peeling or cracking or discolouration of insulation. Blow out the motor winding with clean dry air. Free ventilation holes. Insulation resistance. Check insulation resistance to earth & between phases of motors winding, control gear, etc.
52. What are the various protections provided for motors?
For human safety: Earthing of the motor frame
From Faults: HRC fuses. For protection against short circuit faults.
Overload relay for protection against overloads.
No volt coil for protection against low voltage/ No voltage.
Single phasing preventer for protection against single phasing. Circuit breakers
53. Name the different types of circuit breaker?
a) Bulk oil circuit breaker
b) Minimum oil circuit breaker
c) Air breaker circuit breaker
d) Sulphur hexa fluoride circuit breaker
e) Vaccum circuit breaker
f) Earth leakage circuit breaker
54. What is a circuit breaker? Circuit Breaker is a device capable of making and breaking a circuit under normal as well as under abnormal conditions.
55. Explain maintenance activities carried out on L.T switch gear/Bus bar?
a) Switch OFF panel board and blow out dirt through inside panel and switches.
b) Check & tighten terminals at the Bus bar & switches.
c) Check cable entry for provision of proper insulating bushes at bus bar & switches.
d) Check and clean pitted contacts, check for any overheating/flash marks and searches for causes.
e) Check and ensure proper earthing to bus bar and switches. Check and ensure bus bar neutral is rigidly earthed.
56. Define and discuss the following ratings of A.C circuit breaker a. Rated short circuit breaker current: The rated maximum interrupting current/breaking current is the RMS value of 3-phase current which can be interrupted supply by the circuit breaker under fault/short circuit occurred. The value of maximum breaking current given by the manufacturer should not be exceeded. This refers to the rupturing capacity of CB for breaking maximum short circuit current under fault/short circuit condition of safety (Rupturing capacity of CB is generally in MVA). Here safe interruption means that the time of interruption of CB should not exceed the rated interruption time of CB to avoid damage to the loads. At the same time CB should be able to withstand for the instantaneous over loads. b. Rated short circuit making current: The rated making current is the maximum RMS current against which the breaker is capable of closing and immediately opening without welding of contacts or any other damage.
57. Describe the following. 1. Temperature rise test: - In this test the rated current through all three phases of switchgear is passed continuously for a period till a steady state condition is achieved. Temperature rising at different points is measured and should not be more than 50 degrees centigrade under any circumstances.
2. Mill volt drop test:- This test is used to measure the contact resistance of whole of CB. The voltage drop across the breaker pole is measured for different values of dc current. The voltage drop gives a measure of resistance of current carrying part and contacts. The dc current should be more than 100 amps and less than rated current.
3. Insulation resistance measurement
4. Mechanical endurance tests:- A CB should open and close at the correct speed and perform such operations without mechanical failure. Hence the breaker mechanism is subjected to a mechanical endurance type test involving repeated opening and closing operations. Out of 1000 such operations, 50 Nos are to be operated by energizing the relay. It should work satisfactorily without failure and without requirement of adjustment to the operating mechanism. Then only it is considered that the CB is passed Mechanical endurance test.
5. No load mechanical tests:- Mechanical tests on High voltage CBs are conducted without current and voltage in the main circuit for 1000 no: of operations of opening and closing. There should not be any mechanical failure of contacts and mechanism. Out of 1000, 100 operations are done by connecting main circuit contacts in service with trip circuit. Then only it is considered that CB is passed under this test.
6. Routine test :- Once a particular design is found satisfactory, a large number of similar circuit breakers are manufactured for marketing. Every CB is then tested before putting in service. These tests are known as Routine tests.
7.Type test :- Any equipment when designed to certain specification and is fabricated needs testing for its performance. The general design is tried/tested and the results of such tests conducted on one selected breaker and are thus applicable to all others of identical construction. These tests are called type tests.
EARTHING
58. What is the object of earthing? The object of earthing system is to provide a surface under and around a station, which shall be at a uniform potential (nearly zero or absolute earth potential). This earth surface should be as nearly as possible to the system. This is in order to ensure that, all parts of apparatus other than live parts and attending personnel shall be at earth potential at all times.
59. What are the advantages of earthing? Reduced operation & Maintenance cost Reduction in magnitude of transient over voltages. Improved lighting protection. Simplification of ground fault location. Improved system and equipment fault protection. Improved service reliability. Greater safety for personnel & equipment. Prompt and consistent operation of protective devices during earth fault.
60. What is an earth Electrode? It is a metal pipe, rod or other conductor which makes an effective connection with the general mass of the earth.
61. Name the equipment used for measuring Insulation resistance and Earth resistance and the units? Insulation resistance – Insulation megger, units – Mega ohms. Earth resistance-Earth megger, units – ohms.
62. Give the maximum Earth resistance value? Large power station - 0.5 Ω Major power station - 1.0 Ω Small substation - 2.0 Ω In all other cases - 8.0 Ω
63. What are the factors affecting earth resistance? The resistance of earth system depends upon the following factors:
1. Condition of soil
2. Temperature of soil
3. Moisture content of soil
4. Size and spacing of earth electrodes
5. Depth, at which the electrode is embedded
6. Material of conductor
7. Quality of coal, dust, charcoal and salt in the earth electrode pit 8. No. of electrodes connected in parallel
64. What are the methods of improving earth resistance? The earth resistance can be considerably reduced by digging around the earth electrode to a depth of 1.5 or 1 meters, cleaning the surface of the earth plate or pipe of rust, filling with charcoal soaked in salt solution.
65. Why is Earthing of electrical apparatus necessary? It is well known that the metallic frames of all electrical equipments should be solidly connected to earth to drain away the faulty current (Earth leakage) quickly so that fuse will be blown or Circuit breaker is tripped and to keep the frame at earth potential to achieve safety to the equipment as well as the staff.
66. Enumerate the checks to be carried out on Earth connections? Half Yearly check list:
1. Earth wire joints: Check for proper continuity.
2. Earth clamp bolts & nuts in earth pit: Check for proper contact of earth clamps, slackness, rust & dirt.
3. Earth pit: Check for general condition including dryness.
4. Earth resistance: HT installations: Measure the eath resistance the values shall be main earth 1 ohm and isolated earth 8 ohm. Earth pit no, earth resistance value and date shall be painted on vertical surface of earth pits. Annual Check list :
1. Earth Resistance: LT installations: Measure earth resistance the values shall be main earth 1 ohm and Isolated earth 8 ohm. Earth Pit No, Earth Resistance value and date shall be painted on vertical surface of earth pits.
2. Earth Pits : Check up the electrode for proper earth continuity.
67. Explain the procedure for Measurement of Earth Resistance by 3 point method? By a portable megger earth tester: In making measurements under this method, the terminals P1 and C1 of the instrument are strapped together and connected to the spike (electrode) under test. The terminals P2 and C2 are connected to two auxiliary spikes driven at spacing large enough not to cause mutual interference between the fields of the different electrodes. The depth of insertion of these spikes must not exceed onetwentieth (1/20) of their spacing distance. The megger reading gives directly the electrode resistance.
MEGGER EARTH TESTER C P POTENTIAL SPIKE CURRENT SPIKE EARTH ELECTRODE E E Sub-station
68. Draw the lay –out diagram of a 11kV/440V sub-station ?
69. Name the various electrical equipments available in a sub-station?
1. Transformer
2. Isolator
3.Lightening anester
4. Bus-bar panel 5. Circuit breaker
6. D.G Set
7. Battery charger 500kV A
70. What are the various details to be entered in a sub-station log book? HT.Side
1.Voltage
2. Current
3.Power factor LT.Side
1. Voltage
2. Current
3. Temperature reading of transformer
4. D.G.Set operting voltage and current, time of operation, temperature
5. Shut down
6. Failures & attention to faults
71. What are the safety items to be available in sub-station.
1. Sand bucket with sand.
2. Fire extinguishers.
3. First Aid Box with medicine.
4. Artificial respiration chart.
5. Ladders.
6. Safety earthing chains.
7. ‘Men working’ caution boards.
8. ‘Danger’ caution Boards.
9. Safety Helmets.
10. Safety belts.
72. Describe briefly the purpose of each of the following in Electrical Sub-Station.
i) Lightning Arrestors: A lightning arrestor is a device which protects transformer and for other electrical Apparatus from an over load of electrical voltage. This overload can occur either because of lightning or improper switching in the circuit. The lightning arrestor provides a path over which the overload can pass to the ground before it has a chance to attack and seriously damage the transformer or other equipment
ii) Shielding wire: Its main function is to provide shielding to the transmission line conductors and low height towers against direct strokes of lightning. The shield wire / ground wire increases the potential of the conductor and reduce the surge stress on the insulator due to its capacity coupling.
iii) Metal (Ballast) in substation yard: It is used as a safety measure Due to metal (Ballast) spread in the substation, hazards and deterioration of equipment on account of stagnation of water is reduced. The growth of grass is considerably reduced
73. Name the functions of the following in a sub-station.
(i) Potential Transformers: Potential transformer is used to measure the high voltages in a substation in conjunction with standard low range voltmeters, It also facilitate to operate relays or pilot lights whose ratings are very low. These transformers are extremely accurate ratio step down transformers. (ii) Current Transformers: These transformers are used with low range ammeters to measure currents in high voltage ac circuits. In addition to insulating the instruments from the high voltage line they step down the currents. (The range of the ammeter is increased) in a known ratio.
(iii) Batteries: Batteries are used in a sub-station for feeding supply to control, protection and indication circuits. They are also used for operation of circuit breakers and interrupters and motor operated isolators. They are also used in remote control centre.
(iv) Isolators with Earthing heels: These are used for making and breaking a circuit in off load. The isolators are designed to operate without load. The isolators having an Earthing arrangement such that in the event of opening/switching off a circuit breaker one of the circuit is earthed automatically which is also an additional safety aspect.
74. Write the five essential steps involved in effecting shut down. Before issuing permit –to-work in writing to the official-in-charge of the working party, the Authorized official shall personally effect the shutdown. The procedure involves 5 essential steps as detailed below.
(a) First step:- Identify the electrical circuits feeding the equipment or the area concerned remembering the possibility of alternative feeds as in the case of parallel feeders or different supplies such as AC 3-phase,4-wire bunglow supply mains, 230 volts street lighting mains, pump control mains etc., running on the same alignment or in close proximity to each other.
(b) Second step:- Cut off the supply to the circuit or areas required by opening the concerned control switches. In case of AC 400 volts, 3-phase,4-wire circuits or 3-wire circuits, the neutral link should be opened, as this is liable to assume a potential above earth under certain conditions.
(c) Third step:- To prevent the lines being re-charged inadvertently, the switch concerned should able locked in the ‘OFF’ position, or where there is not possible the control fuses in the switch should be removed and kept under lock and key by the authorized official. In the case of circuit breakers, they should be racked out and locked, the key being retained under the personnel custody of the Authorised Official. Lastly a “men at work” Caution Board should be hung up on the switch or circuit breaker concerned.
(d) Fourth Step:- To ensure that the supply has been correctly cut off, each and every conductor should be tested for supply by means of a testing device. In the case of 400 volts,3-phase,4-wire AC lines, two lamps of equal wattage connected in series shall be used. The testing device should be checked on a live line, before and after the test, to ensure that its indications are reliable.
(e) Fifth step:- Finally, to ensure safety under all conditions, the dead lines including the neutral conductor should be solidly earthed, by means of an approved Earthing clamp or flexible wire having sufficient section. This should be done on both sides of the point where work is to be carried out.
75. What are the items to be checked on 2 /4 / 6 pole structure. Briefly mention the nature of checks to be carried out on the structure?
1. Structure :
a. Check for leaning.
b. Check for any birds nests- Remove if any
c. Paint the structure once in 5 years (Last done date)
2. Anticlimbing Device: Check and ensure availability
3. HT Danger board: Check and ensure availability
4.Insulator: Check of chipped / cracked insulator.
5. Jumpers:
a. Check the condition for oxidation and flash marks & for strands cut.
b. Check and ensure provision fo standard PVC insulation sleeves for all Jumpers.
6. Lighting Arrestor: Check the condition for flash over marks/ cracks.
7. Bird guard lacing: Check the condition.
8. Earth connections: Check for the condition of earth connections for:
i. Structure
ii. Lighting Arrestor(Ensure connections to separate Earth pit)
iii. AB switches and also to its operating handle.
iv. Transformer body and neutral (Double earth with 4 SWG GI wire or flat)
9. A.B. switches:
i. Check for oxidation of contacts of AB switches. ii. Check the locking arrangements and attend.
10. H.T. Fuses: Check the condition and ensure proper rating of standard fuse element is used.
11. Spare HT cable: Check the condition of spare HT cable and cable termination. Spare cable should be suitably supported and terminals to be earthed.
12. APDISCOM Supply point: Check the APDISCOM structure, Metering Cubicle and report to APDISCOM officials if any defect is noticed.
76. What are the different types of insulators used in OH lines? Pin insulator, shackel insulator, stay insulator, reel insulator.
77. Explain the maintenance checks to be carried out on O.H line.
1. Posts : Check the alignment for lean posts. Ensure trimming of infringing tree branches.
2. Cross arms and stay clamps : Check the condition of cross arms, stay clamps and ensure for proper fixing and for proper spacing. Bird Nest if any on cross arms shall be removed.
3. Overhead lines and guarding wire: Check the overhead lines, guarding wires for sag and ensure tightness.
4. Insulators : Check all insulators for cracks and clean thoroughly.
5. Jumpers: Check and clean all the Jumper connection at incoming, out going, tapping point’s and at cut point’s and ensure tightness. Check the condition of jumpers
(1) For oxidation and flash marks.
(2) For strands cuts.
6. Earth Connection : Check and clean all the earth connections and ensure for tightness and continuity, and also ensure all the cut point posts, stays are earthed. Measure and record the individual and combined earth resistance values.
7. Stay Arrangements: Check the studs and stay arrangements and ensure for proper fixing of clamping and for load tension.
8. Conductor: Check it for cut in stands and damage of conductor.
9. Service tapping: Check and ensure proper connections of service tapings. Check and ensure proper Tension in Service Tapings.
78. During maintenance what items are to be checked on U.G cables.
1. Check the insulation values of cables once in a year.
2. Check underground cables near the poles / structure for any damages and also the condition of vertical protection pipe.
3. Check for proper earthing of cable armored and cable protection pipe.
79. What are the maintenance aspects to be taken care of oil used in transformer?
1. Oil level should be checked at frequent intervals the cause of any serious loss of oil investigated. 2. All leaks should be repaired as quickly as possible
3. Oil for topping up should comply with relevant standard specification preferably it should be from the same source as original oil. Samples of the oil should be taken at regular intervals and tested for dielectric strength, acidity and crackle records of these together with top oil temp, should be kept. 80. What is meant by power factor in A.C. circuit?
(a) The ratio of real power to the apparent power is called power factor. Power factor = Real power Apparent power
(b) Power factor is the cosine of angle between voltage and current. P.F. = Cos ᶲ
(c) The ratio of resistance to the impedance is called P.F. P.F. = resistance Impedance
81. What are the disadvantages of low P.F.? The following are the disadvantages of low power factor. 1. As the apparent power increases for a given power load at a constant voltage, the line current increases. This again causes increased voltage drop in the line and thus decrease in terminal voltage across the load.
2. Due to reduced voltage, the induction motor will accelerates slowly and will take higher current to compensate for the load torque.
3. Due to decreased voltage, the heat output of electrical furnaces, heaters reduces
4. The under grounded insulated cables are heated more and thus insulation is weakened.
5. The capacity of switch gears and fuses must be increased,
6. The transmission line drop increases and efficiency goes down.
7. Output of the incandescent lamp decreases.
82. What are the regulations of power line crossings for electrified territory? and Explain the procedure of modifying power line crossings in case of new electrification of tracks between Railways and State Government. These regulations apply to Electrical Over head lines and on under ground Cables crossing Railway Track.
1. UPTO AND INCLUDING 11 KV NORMALLY BY CABLE
2. ABOVE 11 KV AND UPTP 66 KV 14.10 METERS
3. ABOVE 66 KV AND UPTP 132 KV 14.60 METERS
4. ABOVE 132 KV AND UPTP 220 KV 15.40 METERS
5. ABOVE 220 KV AND UPTP 400 KV 17.90 METERS
6. ABOVE 400 KV AND UPTP 500 KV 19.30 METERS
7. ABOVE 500 KV AND UPTP 800 KV 23.40 METERS
The minimum safe clearance between the height of a a crane jig highest point and lower crossing conductor shall be as under;
NORMAL SYSTEM MIN. SAFELEARENCE VOLTAGE IM METERS 33 KV--- --- --- ---
1.50 66 KV--- --- --- --- 2.00 110 KV --- --- --- 2.25 132 KV --- --- --- 2.50 220 KV --- --- --- 3.50 400 KV --- --- --- 6.00 500 KV --- --- --- 7.25 800 KV --- --- --- 11.50
PROCESSOF POWER LINE CROSSINGS ON RAILWAY TRACK:
83. What is meant by low, medium, high and extra high voltages?
84. How the Vertical and Horizontal clearances of power line crossings are to be measured. Explain permissible limits of vertical clearances up to 132KV EHT power line crossings?
The horizontal clearances can be measured by means of measuring tape i.e., between the centre of track and nearest mast/pole/tower on both the sides of the track. It can also be measured by a second span of the power line crossings on both sides of the track. Vertical clearances can be measured between centre of the conductor and ground by providing a plumb off with Rope at the centre of the conductor of the power line crossing/guarding.
85. What are the different types of wiring adopted for house hold wiring? Shich system is now adopted in Indian Railways?
1. Cleat wiring
2.Caring and copping
3. Conduct wiring
4. Metal sheathed wiring
5.CTS or tough rubber sheathed
6. Mineral insulated wiring
7. Now in Indian Railways casing and copper conduit wiring is employed.
86. What are the Classification of insulators? Sl.No. Class Max. Safe temp Description of insulation 1. 2. 3. 4. 5. 6. 7. Y(Formerly 0) A E B F H C 90◦C 105◦C 120◦C 130◦C 155◦C 180◦C Above180◦C The insulation of this class consists of materials such as cotton, silk, paper with out impregnation, etc. Class A insulation consists of materials such as cotton, silk, paper immersed with oil, etc. The insulation of this class consists of materials of better quality than Class A materials such as leatheroid, paper, empire cloth, fibre, etc. Class B insulation consists of materials such as mica, glass fibre, asbestos, etc. The insulation of this class consists of materials of better quality than Class B insulation, The insulation of this group consists of materials such as silicone elastomer, and combinations of materials such as mica, glass fibre, asbestos, etc. Class C consists of materials, such as mica, porcelain, glass, quartz, etc.
87. Name the parts of a fuse Ans. Fuse wire, Fuse carriers, Fuse Carrier Contacts, Fuse Base, Fixed Contacts. 88. Why should we separate power & light circuit? Ans. Power circuits are separated from lighting circuits due to the following reasons:
(i) Faults such as over loadings, short circuits, etc. Commonly occur on power circuits which can cause unwanted disturbances to lighting circuits if they are connected on the same supply mains.
(ii) Power circuits are designed for more voltage drop than lighting circuits which reduces the illumination output of the lamp.
(iii) The life of the lamp decreases with much fluctuation of voltage on the line.
89. Explain the the Insulation resistance test between conductors and between conductor and earth in a wiring installation? Draw a rough diagram?
Ans. Before performing the insulation resistance test of complete installation, the main switch should be put off, all the fuses should be intact in the distribution box, and the lamps (i.e. load) and all the switches should be put ON. One terminal of the megger is connected to the earth wire of the supply or to a water pipe and the other terminal (L) of the megger is connected to one live wire and together with the neutral of the circuit as shown in Fig. Then the handle of the meggar is rotated at its normal speed and the reading on the scale is noted. This reading is the insulation resistance between the conductors and the earth. If the needle of the meggar shows zero reading, it means that there is a direct connection between the conductors and the earth and that should be removed before conducting the next test. The reading of the megger should not be less than 50 /no. Of outlets. In general 1MΩ insulation resistance may be considered as sufficient for the complete installation. Insulation Test between Conductors: This test is conducted to find the value of the insulation resistance between live and neutral conductors and also to locate a short circuit if any in the complete installation. The wire connected during the previous test should be removed with the fuse terminal together with neutral link as shown in Fig. All the lamps should be removed and the main switch should be put OFF. All the fuses should be intact and all the switches should be ON. The megger terminals should be connected across the two main fuse terminals of the installation. The handle of the meggar should be turned at normal speed. In this test also the result should not be less than 1MΩ. This is the insulation resistance between live and neutral conductors. However if the reading is zero, it means there is a short circuit in the wiring which should be removed. This test should be performed only if the result of the last test is found satisfactory. If there is any fault in the first test, that must be removed. QuestionPaper.Org 92 90. What should be the height of the following: (1) Single pole switch, (2) Wall socket, (3) Batten wiring (4) Ceiling fan, (5) Power wall socket Ans.(1) 1.5 metres. (2)1.5 metres (3) 2.3 metres (4) 2.75 metres (5) 0.33 metres 93. What tests are to be conducted a) while a wiring is in progress b) After wiring is completed? a) While house wiring is in progress 1) Continuity test of wiring. 2) Testing of polarity of single pole switches. 3) Insulation resistance test between conductors. b) After wiring is completed. 1) Insulation resistance test to earth. 2) Earth resistance test. 94. What should be the rating of megger used for measure I.R of circuit? The minimum voltage rating= 2x rated circuit voltage ex. For house wiring, Voltage rating of D.C megger=2x 250V=500V DC 95. What is the allowable min insulation resistance of house wiring? One mega ohm. Pumps 96. What are the different types of pumps used in Railways? The different types of pumps used in Railways are, Submersible pumps Jet pumps Centrifugal pumps Mono-bloc pumps Rotary pumps Mono-sub pumps 97. What are the main problems experienced during operation of a centrifugal pump? Pump not starting. No liquid delivered. Not enough liquid delivered. Pump discharge pressure islow. Pump looses prime after starting. Pump overloads driver. Excessive vibration. Bearing overheat. Bearing wears rapidly. 98. Describe the constructional features of centrifugal pumps. The centrifugal pump consists of the following main parts. QuestionPaper.Org 93 1. Bed plate: This may be of cast iron or welded steel which has provision for passing of dowel locating pins driven through the pump and motor legs for easy assembly and correct alignment. 2. Pump Casing: It is made of cast iron and may be split horizontally to enable removal of the impeller and spindle. 3. Impeller: This is made up of close grained cast iron or cast steel . to eliminate rusting, impellers are made of gun metal. They are hydraulically and dynamically balanced. 4. Spindle: This is made of steel. To reduce the leakages, hurts collars, gun metal sleeves and bronze neck rings are used. 5. Stuffing Box and Gland Packing: This serves two purposes – on the suction side it prevents leakage of air and on the delivery side leakage of water under pressure. It has gland bolts, packing material. 6. Bearings: These may be of ball, roller or sleeve type. 99. Explain the working of centrifugal pump. The working of centrifugal pump is based on the principle of centrifugal force. Hence it is named as centrifugal pump. This type of pump in its simplest form comprises an impeller rotating in a volute casing so that liquid/water entered into the centre of impeller and discharged at the periphery resulting into development of vacuum on suction side and more water/liquid flows into the impeller and constant discharges can be obtained. Priming is very important for centrifugal pump to avoid entry of air in the system due to centrifugal force. 100. What maintenance checks are carried out in pump? Quarterly check Pump noise Pipe connections and nut/bolts Foot valve strainer Moving parts for lubrication Yearly check Remove impeller, replace if vanes are worn out totally Replace shaft sleeves, if worn out Replace gland packing, if worn out Replace any other worn out part Replace mechanical seal if damaged. 101. What are the precautions you take while installing. (a) Submersible pump: Motor of the submersible pump to be filled up with adequate quantity of clear, cold water before coupling to the pump and ash should not enter. b) Pump set should not be lowered to the bottom most point of bore well. c) It should be lowered up to the above mud level only. d) Proper coupling between each GI pipe and pump sets should be ensured. e) Avoid cable joints and bents. f) Provision of Water level guard should be fixed at the coupling between motor and pump. QuestionPaper.Org 94 g) The gap at the mouth of the bore well around submersible pump should be closed. h) Supporting clamps should be mounted properly. (b) Horizontal Centrifugal pumps: a) Foundation and foundation bolts for pump and motor should be ensured as per the specification. b) Proper alignment between motor and pump should be ensured. c) Proper functioning of non return valve should be ensured. d) Anchoring of suction pipe and priming of pump should be ensured. e) Lubricating bearing and tightness of gland packing should be ensured. 102. What are the functions of the following in a pumping installation. (a) Strainer: It is fixed in the suction side which prevents the entry of foreign matter in the system. (b) Foot Valve: It is fixed at the bottom of the suction pipe which is useful to maintain liquid in the suction pipe while in operation and stationary conditions. Entry of foreign matter in the pumping system can be prevented by providing a suitable mesh around the foot valve. The foot valve has a hinged leather faced flap which lifts up during the normal operation, and drops and closes the opening when pump stops. (c) Sluice valve: It is provided in the discharge pipe line which is used at the time of replacement of pumps. In normal operations this should be kept opened. This is generally provided where a pump is installed below the water level in a reservoir which gives positive feed in to the pump. (d) Non-return valve: This should be of robust design and strong enough to withstand the heavy shocks caused by water hammer action, when the pump is shut down, and protects centrifugal pump and the foot valve. This valve is provided in the delivery side of the pipe line. (e) Vacuum and pressure gauges: Vacuum gauge is used to measure the pressure below that of atmospheric pressure either in feet or lbs/inch. Pipe connection to the gauge is taken from the suction inlet to the pump pressure gauge is provided on the delivery side of the pump to measure out put water pressure of the pump. 103. Describe the merits and demerits of submersible pumps over vertical shaft pumps. Submersible pump can be installed in the bore wells which are not exotically vertical where as vertical shaft pumps cannot be installed in such cases. 2) The installation of a vertical pump requires the services of an experienced mechanic since alignment of column pipe and rotating shaft should be very accurate. 3) In case of oil lubricated vertical pump special attention is required and maintenance cost is also more than submersible pump. 4) Submersible pumps are more reliable than vertical shaft pumps which has got various mechanical elements. 5) Submersible pumps can be operated by remote control very easily. 6) Dry running of the submersible pump leads to burning of motor. 104. What are the basic criteria for selection of (i) Submersible QuestionPaper.Org 95 pumps (ii) Vertical shaft pumps. Criteria for pumps selection is : 1. Nature of liquid, water (Raw or tread) or chemicals to be handled. 2. Type of duty required i.e., whether continuous, intermittent or cyclic 3. Present and projected demands and pattern of change in demand. 4. The details of head and flow rate required 5. Type and duration of the availability of the power supply 6. Selecting the operating speed of the pump and suitable drive/driving gears. 7. The efficiency of pumps and consequent influence on power consumption and the running costs 8. Possible permutations of the parameters of the pumping system, in lading capacity and number of pumps (With standby) combining them in series or in parallel 9. Options of different modes of installations and their influence on the civil and structural costs, on the case of operation and maintenance and on over all economics. 105. Indicate the type of pumps you select in the following application duly justifying your selection. i. Bore well pump for individual domestic water needs = Submersible pump for more depths and jet pumps for less depth. ii. Open well near river beds for water supply to colonies, industrial and commercial needs of high suction lift =Multi stage Centrifugal pumps iii. Bore well pumps at small Railway premises = Submersible pumps iv. Open well pump with suction lift of 5 M for Divisional HQ Railway premises = Monoblock pump v. Pump for Transfer of HSD oil from drums to Engine tank = Rotary pump 106. i. Name important data to be collected for designing pumping installations. ii. Calculate the Rating of pump motor, used for pumping 120 G.P.M. of water against total head of 212 feet? Assume efficiency of pump as 70%. Maximum daily consumption of water for the present and anticipated increase consumption for the next five years for domestic, commercial, industrial use on the base of yardsticks approved. On the above basis hourly requirement can be calculated and curve can be drawn. Type of fluid to be pumped Type of source in reservoir / sump, well (Including depth) etc., and then hydraulic data recorded during the last 15 to 20 years. Location and capacity of Overhead tank can be derived from the above points. Route and diameter of the pipe line by considering the utilization for different places and various types. Times of requirements. Power supply availability Sanction for provision of stand by prime movers. ii. Ans. QuestionPaper.Org 96 Total Head = 212 feet Water to be pumped = 120 GPM Therefore Work done required = 120 x 10 x 212 (10lb/gallon) Efficiency= 70% HP= 120 x 10 x 212/0.7 x 33000 = 11 HP. 107. Briefly explain the Daily and Half yearly checks to be carried out on mono bloc pumps. Daily Maintenance: 1. Gland Packing: Leakage through Gland packing. 2. Bearings: Bearing temperature 3. Sound: Whether any under noise or vibration is present. 4. Readings: Pressure, Voltage and current reading. Half Yearly Maintenance: 1. Free movement of gland of the stuffing box. 2. Cleaning and oiling of the gland-bolts. 3. Inspection of packing and repacking if necessary. 4. Alignment of the pump and the drive. 5. Cleaning of oil-lubricated bearings and replenishing fresh oil. If bearings are greaselubricated, the condition of the grease should be checked and replaced to correct quantity, if necessary. 6. An anti-friction bearing should have its housing so packed with grease, that the void spaces in the bearings and the housing be 1/3 to ½ filled with grease. A fully packed housing will cause the bearing to overheat and will result reduced life of the pump. TARRIF 108. What is Tariff? Name the different categories of Tariff under which power are obtained from distribution authorities? Electrical Tariff represents the basis on which charges are recovered from the consumers for supply of electricity. The main objectives of the tariff is to distribute equitably the cost of supplying electrical energy among the various classification of use such as lighting, heating, industrial and, bulk supply etc. The different kinds of tariff in common use are as under: Simple tariff Flat rate tariff Block rate tariff Two part tariff Max. demand tariff Power factor tariff Three part tariff Off peak tariff 109. (a) Explain (i) Load factor (ii) Diversity factor. LOAD FACTOR: The load factor is specified with its period viz., daily load factor, monthly load factor or annual load factor. QuestionPaper.Org 97 The annual load factor is defined as the ratio of KWH supplied by the station in a year divided by the product of peak load and 8760 (The no. of hours in a year). Yearly load factor: No. of units supplied in a year --------------------------------- Max. No. of units which can be supplied = No of units supplied in a year --------------------------------- Max. Demand X 8760 Similarly monthly load factor = KWH supplied in a month --------------------------------- Max. Demand X 24 X 30 The value of load factor is always less than 1. The no. of units supplied can be obtained from the summation curve and the max. Demand on half hourly basis or 15 minutes basis can also be obtained from the summation curve explained earlier. Higher load factor means more no of units generated per year. DIVERSITY FACTOR: The diversity factor is defined as the ratio of the sum Of maximum demand of the power stations. Diversity factor: Sum of Max. Demands of each category ------------------------------------------ Max. Demand of the station. The value of diversity factor is always more than 1. The greater the diversity factor, the lesser will be the Max. Demand. Hence the supply organizations try to improve the load factor as well as the diversity factor by inducing the customers to use the electricity during off peak time and they may be charged at lower rates for such schemes. (b) Find the monthly load factor of a sub-station with a M.D. of 5 MVA and average monthly consumption 25,00,000 units. Average P.F. = 0.8. Monthly load factor: KWH supplied in a month ------------------------------- Max. demand X 24 X 30 = 25,00,000/5 x 10 X 10 X 10 X 24 X 30 X 0.8 = 125/14.4 = 0.86 110. The following are the features of HT. category tariff. a. M.D. 80% of CMD or RMD whichever is more. b. M.D. (Penalty) If the RMD exceeds 110% for portion exceeding CMD, MD charges are double the normal MD charges. QuestionPaper.Org 98 c. Energy charges. Recorded energy units or 250 units for kVA of CMD whichever is more. d. P.F. penalty 2 Paise / Unit if the P.F. is below 0.9. e. P.F. discount 1 Paise/unit if the P.F. is above 0.95. f. Meter rent Rs. 1500/- g. MD charges. 1500 / KVA, Energy charges Rs. 420/KWH. Find the energy bill if the joint readings are as follows for 11 kV substation having CMD: 2500 kVA. (a) M.D. = 1200 kVA, KWH=6,00,000 units P.F. = 0.96. i. MD = 80% of CMD = 80% of 2500 = 2000KVA MD = 80 % of RMD = 80% of 1200 = 960 KVA ii. MD penalty = No penalty as RMD is less than CMD MD charges = Rs 1500 x 2000KVA =Rs30,00,000 iii. Energy charges Recorded energy units=6,00,000xRs420= Rs25,20,00,000 is less. 250 units/KVA of CMD=250x2500KVA = 6,25,000 units. 6,25,000 x RS 420 =Rs 26,25,00,000 is more. Power factor penalty =Nil P F discount =1paise/unit x 6,25,000 =Rs 6,250. BILL: Rs 30,00,000+26,25,00,000+1500-6250 = Rs26,54,95,250.Ans. FIRE SAFETY 111. What are the reasons for fire occurrence Enumerate in : 1. Substations:- Due to leakage/spillage of oil from oil drums, Paints and other inflammables etc coming in contact with electrical sparks of burnt switches, cables, short circuit of wiring etc, Anybody throwing a lighted cigarette on the oil drum or used cotton waste causes fire in substation. Flashover from switches, circuit breakers, etc also leads to fire in substations. 112. Why at all a Fire occur At workshop:- i) Improper storing of inflammables like petrol, Diesel, Paints etc and if anybody throws a lighted cigarette on these items or due to electrical short circuit, overheating and burning of cables etc fire occurs. ii) If used cotton waste/oil cotton waste etc are not disposed off properly and any welding arc, grinding material fire, cigarette fire comes in contact with the cotton waste leads to fire. iii) Electrical short circuits, burning of cables etc leads to fire in workshops. At AC /TL coach :- i) Carrying inflammables in the coaches and getting lit by cigarette etc results in fire. ii) Carrying of intoxicated drinks/liquor which when QuestionPaper.Org 99 comes into contact with spark, etc leads to fire. iii) Smoking and throwing the lighted butts etc on the easily combustible material by the passengers will also lead to fire in coaches. iv) Some times unsafe use of stoves in pantry cars leads to fire. v) Using of oversize fuses, under size cables, improper/loose terminal connections, tightness of connections, etc leads to fire in coaches vi) Bypassing of safety items like fuses, relays etc, low insulation resistance causing earth leakage, also leads to fire in coaches. At residence:- i) Leakage of gas cylinder, stove, improper storing of inflammables like petrol, kerosene, diesel etc which can come in contact with sparks or fire. Electric heater when come in contact with clothes, ii) Electrical short circuit, burning of wiring etc leads to fire. iii) Lighted cigarette, beedi etc falling on huts, beds or other Combustible material stored in the residence leads to fire . At office.:- i) Electrical short circuits, burning of cables/wires, etc leads to fire. ii) At the time of burning of old records/papers in unsafe manner and due to wind flow the flames come in contact with combustible material and cause spread of fire. 113. How many types of fire extinguishers are available in your jurisdiction. There are four types of fire extinguishers A class: Soda ash cartridges, water buckets, chemical foam, Halon gasses etc., B class: Chemical foam, Dry powder, carbon dioxide Halon gas C class: Dry chemical powder, carbon dioxide, Halon gas D class: Halon gas, Dry chemical powder, carbon dioxide 114. Classify various types of fires and how do you extinguish them in detail. There are four types of fires classified. They are A type : General fires such as solid materials, cotton, wood etc. B type: Oil fires such as Liquid materials, oil, grease etc. C type: Chemical fires such as fires in gasses D type: Electrical fires such as metallic, electrical etc. For extinguishing the fire use the above mentioned fire extinguishers as mentioned according to their classification in answer ‘G’. 115. Write 5 slogans for (1) Prevention of fire (2) Prevention of accident. Prevention of fire:- i) No Smoking. ii) Do not over load the Electrical equipment iii) Handle carefully the inflammables. iv) No loose connections and Hanging wires. QuestionPaper.Org 100 v) Do not bring naked flame near a battery. Prevention of accident:- i) Be cautious. ii) Handle with care. iii) don’t play with electricity. iv) Don’t lean on switchboards and electrical equipment. v) Use safety items viz., safety belts, helmets etc 116. What are the preventive measures to be taken to avoid Fire accidents in Workshop. ---Use electrical equipments of approved design and from reputed manufacturer. ---They are to be installed properly, by experienced staff who are fully aware of their responsibilities and conversant with the statutory rules like IE rules and regulations for safe working on electric equipments. ---The electrical equipment has to be maintained properly by carryings out periodical inspections and tests to ensure that the equipment is safe. --- The equipment has to be used carefully, taking normal precautions . --- The place of working should be dry and free from inflammable items. ---proper earthing of the equipments is to be done. ---Loose connections and shortcut methods are to be avoided. Hanging wires and bare wires should not be allowed. 117. What action you will take when fire occurs in a HT Sub-Station? First isolate the substation. Switch off all the equipments. Use the fire extinguishers available in substation for extinguishing the fire Send the information to the nearest fire station Inform to the higher official Clear the combustible material if any near the vicinity of the fire. 118. Name the different types of cable jointing kits available. Ans. i. Heat shrinkable jointing kit. ii. Cold shrinkable jointing kit. Iii. Tapex tape type jointing kit. iv. Push on type jointing kit. v. Cast resin jointing kit. 119. On completion of laying, terminating UG cables what are the points to be noted down? Ans. On completion of laying, terminating and jointing of the cables, a plan should be prepared, which should contain the following details of the installation. a. Type of cables, cross-section area, rated voltage. Details of construction, cable number and drum number. b. Year and month of laying. c. Actual length between joint-to-joint or end. d. Location of cables and joints in relation to certain fixed reference points, for example, buildings, hydrant, boundary stones, etc. QuestionPaper.Org 101 e. Name of the jointer who carried the jointing work. f. Date of making joint. g. Results of original electrical measurements and testing on cable installation. All subsequent changes in the cable plan should also be entered. 120. Explain the maintenance procedure on underground cables? The maintenance of cable installation includes inspection, routine checking of current loading, maintenance and care of all cables and end terminations. INSPECTION When ever the cables or joints are accessible as in manholes, ducts, distribution pillars etc., periodical inspection should be made so that timely repairs can be made before the cables or joints actually cause interruption to service. Preventive maintenance in the form of regular inspection of all digging operations by other utilities or persons, carried out in areas they are electric cables exists is of utmost importance. CHECKING OF CURRENT LOADING The life of paper insulated cables is considerably reduced through overloading. It is, therefore, essential to check the loads as frequently as possible to ensure that the cables are not loaded beyond the safe current carrying capacities. The derating factors due to grouping of several cables, higher ambient ground temperature and higher thermal resistivity of soil, should not be neglected. MAINTENANCE OF CABLES Repairs of cables generally involve replacement of a section of the defective cable by a length of new cable and insertion of two straight joints. All repairs and new joint in connection with repairs should be made in the same manner as joints on new cables. In some cases where the insulation has not been damaged severely, or where moisture has not obtained ingress into the insulation, it may only be necessary to install a joint at the point of cable failure. MAINTENANCE OF END TERMINATIONS Visual inspection of all the cable end termination should be carried out regularly for any over heating flashing mark, insulation damage etc. Cable end terminations should be checked for tightness with a suitable torque wrench/spanner periodically. Check the cable support clamps, glands for proper position and intactness. 121. What are the points to be attended during POH of battery chargers? Ans. PERIODIC OVERHAULING OF BATTERY CHARGERS (Yearly) 1. Dismantle side covers, top covers. 2. Blow jet dry compressed air to remove dust and dirt. QuestionPaper.Org 102 3. Inspect the condition of transformer assembly, rectifier assembly, fuse assembly and wiring. 4. Check condition of bus bar heat sink, main diodes. Replace if found damaged/defective. The polarity of silicon diode must be checked before replacement of new diode. 5. Check the condition of transformer winding and other electrical parameter. If the transformer is found defective, take for rewinding. 6. Check the condition of rotary switches, push buttons. Clean and attend them for minor repairs. Replace with new one if found burnt/defective. The terminals of the rotary switch should be kept tightened. 7. Check all fuses and replace with new one if found defective. 8. Remove and clean thoroughly terminal board assembly. Replace components with new one if found damaged/defective. 9. Check the tapping of the transformer and attend damaged portion. 10. Replace burnt-out/defective wires/cables of terminal board. 11. Remove the Ammeter, Voltmeter and send it to test room for overhauling and calibration. 12. Check all joints and connections of primary and secondary winding. 13. Check the insulation and earth resistance of the charger. 14. Paint the control panel, if required. 15. Check the electrical parameters such as voltage, current, temperature rise and record. Also check the performance of the equipment for 4 hours. 122. Enumerate the likely causes for the main fuse blowing out in a battery charging rectifier? Ans. 1. Main fuse blowing out a. Power rectifier diode may be short circuited. b. Wiring may be short circuited. c. Winding may be short/low insulation. Check diodes and replace. Check & rectify. Check the resistance of winding and repair if required. QuestionPaper.Org 103 123. What are the different types of welding plants? Ans. The different types of welding plants are: Arc welding plants,CO2 and plasma welding plants. 124. What will happen if a motor is started with two phases only because of one fuse being blown off? Ans. The motor will not start. 125. What data should be noted while rewinding a motor? Ans. Before starting rewinding, the complete data of the motor should be noted. The data can be divided into two parts: (i) Name plate data: Note down the following details: Make of the motor, No. of phases, Horse power, R.P.M., Voltage, Full-load current, Frequency, Temperature, etc. (ii) Re-winding data: Note down the following details: No. of coils, No. of slots, Turns per coil, No. of coils per group, No. of groups, No. of poles, Coil-pitch, size of wire, No. of parallel paths, No. of conductors in each coil, Connections, Insulation used in slots, Insulation used on coils etc. 126. Name the energy efficient measures adopted in lighting? Ans. i. Use of CFL lamps. ii. Use of T5 fittings iii. Use of LED type fittings. iv. Use of work spot lighting. v. Using of Star rated lamps. 127. What are the advantages of an electronic choke as compared to normal choke? Ans. The advantages are as follows: i. It doesn’t produce any noise and doesn’t blink also. ii. It doesn’t consume more electric power. It saves 33% of electric power. iii. It doesn’t require a choke and a capacitor iv. It starts the tube in less than 1 second. QuestionPaper.Org 104 v. Its weight is low. vi. The choke circuit component can easily be repaired up. vii. It can work on voltage between 100 to 300 volts. viii. It doesn’t get hot. ix. Its life is double. x. It can work on A.C./D.C. source. xi. It gives more light. 128. What is the function of a choke in the florescent lamp? Ans. i. when the starter’s contacts get open due gas glow then the flux of the choke falls rapidly and a surge voltage of about 1000V is developed. The gas discharge glow is started in the tube at this high voltage. ii. when the tube is glowing then it supplies about 110volts to the tube. iii. it regulates the current at a stable rate during operation of the tube. QuestionPaper.Org 105 OBJECTIVE TYPE QUESTIONS ON ELECTRICAL POWER MAINTENANCE 1. The net resistance of a circuit consists of 4 resistances 1,2,3,4 in series is ___________________. 2. The net resistance of a circuit consists of 4 resistances 1,2,3,4 in parallel is ______________ a. 0.58 b. 0.48 c. 0.40 d. 0.50 3. The best conductor of electricity is a. Silver b. Aluminum c. Brass d. Zinc 4. The mercury is a _____________ conductor. a. Solid b. Liquid c. Gaseous d. None of the above 5. Dry air is a a. Conductor b. Insulator c. Semi- conductor d. None of the above 6. The theoretical water column that can be supported by atmosphere at sea level is a. 10 feet b. 24 feet c. 34 feet d. None of the above 7. In centrifugal pump water is admitted into the a. Center of rotor b. Outer periphery of pump c. None of the above 8. In a turbine pump the water enters into the pump from a. Center of rotor b. Outside opening on the casing c. None of the above 9. Which of the following pump require priming a. Centrifugal pump b. Turbine pump c. Submersible pump 10. In a submersible pump the motor is located a. Below the pump b. Above the pump c. In the middle QuestionPaper.Org 106 11. In a centrifugal pump water is a. Permitted to enter into the unit and circulate between rotor and stator b. Not Permitted to enter into the unit and circulate between rotor and stator 12. The bearings in a submersible pump are a. Water lubricated b. Oil lubricated c. Grease lubricated 13. Equipment earthing means a. Earthing of all metal work of electrical equipment other than live parts b. Earthing of all metal work of electrical equipment including live parts 14. System earthing is done to a. Limit the potential of live conductors with earth b. Increase the potential of live conductors with earth c. Decrease the potential of live conductors with earth d. None of the above 15. The meaning of earthing or grounding is to connect the earth point of equipment to general mass of earth by wire of a. Negligible resistance b. Higher resistance c. Low resistance d. None of the above 16. The minimum size of G.I pipe electrode used in pipe earthing is a. 25 mm Dia b. 40 mm Dia c. 50 mm Dia d. 70 mm Dia 17. The minimum distance of earth electrode from a building shall be a. 1.5 m b. 0.5 m c. 2.5 m d. 2.0 m 18. The maximum permissible earth ‘R’ values for major power stations is a. 0.5 b. 1.0 c. 2.0 d. 8.0 19. Earth continuity inside an installer from earth plate to any point in the installation is a. 1.0 b. 2.0 c. 3.0 d. 4.0 20. In maintenance free earthing the electrode is of_________. QuestionPaper.Org 107 21. The earthing electrode shall always be placed in a. Vertical position b. Horizontal position c. Any position 22. The minimum size of earth wire is a circuit / sub-circuit should be a. Equal to size of conductor used in circuit/sub-circuit b. More than the size of conductor used in circuit/sub-circuit c. Half of the size of conductor used in circuit/sub-circuit 23. The minimum no. of earth for earthing a transformer separate a. Two independent earth b. One earth c. Three separate & individual earth 24. The distance between two earth electrodes shall be a. Equal to length & earth electrode b. Twice the length & earth electrode c. No distance need to be maintained 25. The earth resistance should be checked once in a year a. On a dry day during dry season b. On a dry day during wet season c. Can be checked anytime 26. The minimum distance to be maintained between the two electrodes of earth megger when taking reading shall be a. 20 feet b. 40 feet c. 10 feet d. 75 feet 27. While measuring the earth resistance a. It is necessary to disconnect the electrode under test from the installation b. It is not necessary to disconnect the electrode under test from the installation c. Inter connect all the earth electrodes in vicinity 28. The combined Earth resistance of 33kV/11kV receiving station should not exceed a) 1 ohm b) 2 ohms c) 10 ohms d) 20 ohms 29. The combined earth resistance of 11kV/415 V Sub-station should not exceed a) 0.5 ohm b) 2 ohms c) 10 ohms d) 20 ohms 30. As per the present Tariff the minimum power factor of sub-station should be a) 0.8 b) 0.85 c) 0.90 d) 0.95 QuestionPaper.Org 108 31.The minimum clearance of lowest conductor from the ground of 33kV lines, across the road a) 3M b) 4M c) 6.1M d) 14 M 32. The minimum clearance of lowest conductor from the ground of 33 kv lines, along a street a) 5.8 M b) 4.0 M c) 3.0 M d) 14 M 33. The minimum vertical clearance from 11 KV line to any part of building a)2.0 M b)10 M c) 3.7 M d) 6.0 M 34. The minimum Horizontal clearance of 11 kV lines from any buildings a) 1.2 M b) 3.7 M c) 6.1 M d) 10 M 35. The Rod gap on the L.V. side of 11 kV/415V, 250 kVA Transformer is a) 300 mm. b) 100 mm. c) 50 mm d) Rod gap L.A. is not provided for LV side of Transformer 36. The rated voltage of L.A. for 11 kV/415V Transformer protection is a) 11 KV b) 12 KV c)9 KV d) 24 KV 37. For medium sized 11kV/415v, 500 kVA Transformer sub-station, the type of L.A. used are a) Station type b) Line type c) Distribution type d) None of these 38. The line type L.A. used for our 11 kV and 33 kV sub-station are having a standard normal discharge current (peak) a) 5 KA b) 10 KA c) 1.5 KA d) 2.5 KA QuestionPaper.Org 109 39. The span of supports for 11 kV over head lines should not exceed a) 100 m. b) 65 m. c) 30 m. d) 27 m. 40. Minimum insulation value of transformer of 11 kV / 415 V with 1000 V megger a. 200 mega ohm b. 10 mega ohm c. 50 mega ohm d. 100 mega ohm 41. Extra high voltage is more than a. 250 V b. 650 V c. 33 kV d. more than 33 kV 42. Speed of induction motor depends upon a. No. of poles b. Frequency of power supply c. Both a & b d. None of the above 43. Ceiling fan is a _____________ a. Single phase capacitor start & capacitor run motor b. single phase capacitor start motor only c. 3 phase motor d. None of the above 44. In a 11kV / 415 V sub-station the transformer is connected in _______________ to step down voltage. a. Star – star b. Delta – delta c. Star – delta d. Delta - star 45. The reason of drawing high current at the time of starting by an induction- motor is: a) high voltage b) low power factor c) zero back e.m.f. 46. In a three phase induction-motor, the speed of rotor is always lesser than that of stator. 47. A D.O.L. starter is used with squirrel-cage induction-motors up to 5H.P. 48. A star-delta starter is used with slip-ring induction-motors of 5 to 20 H.P. 49. A universal D.C. motor is a series motor. a) shunt b) series c) compound QuestionPaper.Org 110 50. If two transformers have different voltage ratios and their parallel operation is desired then: a) they can not work. b) they will work at different power factors. c) they cannot work on load. 51.In a transformer, the mutual flux links from: a) primary winding b) secondary winding c) both the windings. 52. For a small transformer, the 3-phase connections in use are: a) star-delta b)delta-star c)star-star 53._________ connection combination is used at a sub station to step-down the voltage ? a) star-delta b)delta-star c) star-star 54. The silica jelly used in the breather of a transformer stops the moisture to reach the insulating oil. a) rain water b) dry air c) moisture 55. If the pump fails to start the likely cause/s is /are a.) Fuses blown. b). Short circuiting. C). Heavy load on the pump d. )All of the above. 55. A delta-star connected 3-phase transformer is used for high voltage transmission. 56. The distance between two earth-pits should be _____________ 57. At ________ distance an earth-point should be installed from a building. 58. 1 horse-power (H.P.) is equal to _______watts. 59. The power consumption of a 100 watts lamp used 10 hour daily will be: a) 2 units b) 1 unit c) ½ unit d) 5 units 60.Commutator converts A.C. into D.C. 61. In a self-excited generator residual magnetism is necessary for producing the induced e.m.f. 62. The commutator is made of copper metal. 63. A D.C. shunt generator is used for battery charging purposes. 64. A D.C. over compound generator is useful for transmitting electrical power up to distant places. QuestionPaper.Org 111 65. A series motor is always started on load. 66. A starter protects a motor against he damages caused by a heavy current flow. 67. If the field or armature terminals of a d.c. shunt motor reversed then the direction of armature‘s rotation will change. 68._____________ Is the frequency of main-supply in our country. 69.1 µF is equal to a) 10-6F b) 106F c) 10-3F d)103 F 70. 11 kv HT Power supply is to be availed when the total load exceeds a. 100 KW b. 1000KW c. 75KW d. 56KW 71. The voltage of 11 KV supply is a. 11000V b. 1000V c. 100V d. 33000V 72. The EHT power line crossing means. a. Above 11KV b. Above 33KV c. Above 132KV d. Above 400KV 73. Guarding is required for the power line crossings of following Voltages. a. Up to 11KV b. Up to 33KV c. Up to 132KV d. Above 132KV 74. Tracks not likely to be electrified in the foreseeable feature come under category of (a) Category ‘A’ (b) Category ‘B’ (c) Category ‘C’ (d) Category ‘D’ 74.Radiator is used for cooling of diesel engine. 75. Power in the diesel engine is the ratio of work to time. 76. Diesel engine overhauling is recommended after every 25000 working hours. 77.Governor in a diesel engine is used for maintaining the given speed by adjusting fuel supply at various loads. 78.Vibration dampers are used for controlling the tort ional vibration of the crankshaft 79.Air filters are classified as dry type and oil type. 80.Unit of work in MKS system is Joule . 81.Carburetor is used for vaporizing petrol and mix it with air. 82.BEE is acronym for Bureau of Energy Efficiency. 83.The Electricity act 2003 has come into effect on 10.6.02. 84.RLDC stands for Regional Load Despatch Centre. 85.The requisition for shut down is submitted on form No.EE243. 86.The requisition for permit to work is submitted on form No.EE244. QuestionPaper.Org 112 87.Certificate for clearing shut down is issued on form No.EE245. 88.Competency Certificate ‘_C_’ is issued by SSE for skilled electrical staff. 89.The currency of Competency Certificate ‘C’ is 5 years. 90. The size of wire should be used as earthing-wire in house-wiring is ________________. 91.A. 7/20 size cable contains ____wires each of_______. 92. In diesel engines _________________ is compressed inside the cylinder. 93. In diesel engines the ______________ is injected which burns itself due to high temperature of compressed __________________. 94. Besides the use of D.G sets as a standby power supply arrangement they are also used in _________ in Railways. 95. During priming of pump __________________ valve is kept open to permit air to escape from the pump section. 96. In a centrifugal pump air leakage may take place either in ____________ or in ________________. 97. _________________ is provided in cable to avoid mechanical injury to the cable. 98. The different types of power cables classified on the basis of insulation used are ______________, ______________, _____________. 99. The minimum size of copper plate electrode used in earthing is -----------------. 100. The minimum size of galvanised iron and steel plate electrode used in earthing is ------ ----------- 101. The minimum size of G.I pipe electrode used in earthing----------- . 102. The minimum clear space required in front of switch board is___________ metre. 103. The minimum height of fencing to protect outdoor sub-station is _________metre. 104. The capacity of water storage tank with efficient standby pump should ______ of the maximum water consumption in 24hrs. 105. The capacity of water storage tank without standby pump should ______ of the maximum water consumption in 24hrs. 106. The output capacity of pump should be capable of supplying in _______ the normal quantity of water required in 24hrs. 107.Minimum clearance between highest traction conductor and lowest crossing conductor for OH Crossing voltage between 132 KV and 220 KV is 15.4 m 108. Minimum horizontal distance between power line crossing tower and track shall be Height of the tower + 6 m 109. Power line crossing tower should be earthed with an earthing electrode (T / F) TRUE 110. Guarding wire is not required if the system voltage of power line crossing is above 33 KV. 111.Jointing is permitted in the crossing span (T / F). FALSE 112. Inside station limits for B.G. line minimum height above rail of lowest crossing 113. Conductor for system voltages above 66 KV and upto 132 KV at mid span is 14.6 m 114. 11 KV crossing can be overhead type (T / F) FALSE QuestionPaper.Org 113 115. If crossing is provided with a guarding, a minimum clearance of _2.0 m shall be maintained between the bottom of the guard wire and highest traction conductor. Objective Type: Sl.No Item To be filled 1. Transformer Secondary Volts = Primary Volts x ( ) Primary turns. Secondary Turns (Primary Amps. Secondary. Amps. Secondary turns). 3. Breather is packed with material Silica gel (Silica Jel, Oil) 20 KV 4. The minimum BDV of transformer Oil is 40 KV (40 KV, 50KV, 55 KV) 5. Maximum permissible resistance of major substation 1.0 (1, 2, 8) 6. Maximum permissible resistance of small substation. 2.0 (1, 2, 8) 7. Earth fault relays providing against Earth fault (Earth fault, Core heating full of oil level) 8. Over current relays providing against Over current (over current. Over voltage Earth fault. 9. Low Voltage is not exceeding 250 V (250V, 650V, 33 KV) 10. Medium Voltage is not exceeding 650 V (250V,650V, 33 KV) 11. High Voltage is not exceeding 33 KV (250V, 650V, 33 KV and more than 33 KV) 12. Extra High Voltage is more than More than 33 KV (250V,650V, 33 KV and more than 33 KV) 13. MCCB is ---------- case circuit breaker. Moulded Miniature, Moulded). QuestionPaper.Org 114 QUESTION BANK FOR OFFICIAL LANGUAGE 1. When an employee is deemed to possess proficiency in Hindi? The employee is deemed to be proficiency in Hindi a)If he has passed Metric or equivalent or higher examination with Hindi as medium b) If he took Hindi as an elective subject in a Degree or Equivalent or higher examination c) If he declares that he possess proficiency in Hindi 2. When an employee is deemed to have acquired working knowledge of Hindi? An employee is deemed to have acquired working knowledge of Hindi a) if he has passed Metric or equivalent or higher examination with Hindi as subject b) if he has passed Pragya examination under government’s Hindi teaching c) Other examinations specified by the government d) if he declares that he has acquired a working knowledge of Hindi 3. What are different steps taken by Railways to implement Hindi in official work? As per article 342 (1) of the constitution, Hindi in Devanagari script will be the official language of the union. Article 343 (2) gives the president, powers to authorize the use of Hindi in addition to English. Under this power, president laid down some orders in 1952. Later, it was decided to continue using English and the official language act of 1963 was passed. This act was amended in 1967 to incorporate the assurances of Prime minister that English will continue to be used by a state for its communication with union till that state likes. In 1976, some more rules were framed under the official language rules like dividing the union into three regions for implementing the official language and incentives are introduced for using Hindi in official use, passing of Hindi examinations and others. 4. What incentives are given for passing various Hindi examinations? Passing of Prabodh --- Rs.250/- Praveen --- Rs.250/- Pragya --- Rs.300/- Hindi Typewriting --- Rs.150/- Hindi Stenography --- Rs.300/- Other Hindi examinationsConducted by voluntary bodies --- Rs.300/- Those passed with 60% or above will be given an increment. Special casual leave may be granted for appearing to such examinations. QuestionPaper.Org 115 5. What are the various incentives for use of Rajabhasha? ` 1. Awards for writing books on professional subjects in Hindi --- First prize is Rs.6000/- 2. Railway ministers best essay awards given during the Railway week First prize—Rs.1000/- Second prize – Rs.700/- 3.Group Awards to staff of a department who makes maximum use of Hindi – First prize – Rs.5000/- Second prize – Rs.3000/- Third prize – Rs.2000/-. Each employee gets Rs. 100/- 4. Boards individual Awards to employees for their work in Hindi –Rs. 850 and a certificate of merit given by Railway Minister (w.e.f.1987) 5. G.M’s individual Awards to employees – Rs.300/- and a certificate of merit 6. Awards of noting and drafting in Hindi First prize – Rs.800/- Second prize – Rs.400/- Third prize – Rs.300/- (w.e.f.1-4-98) 7. Incentive to typists and stenographers who in addition to their work in English, do Hindi typing and stenography work, a monthly allowances of Rs. 80/- to typists, and Rs.120/- to stenographers (w.e.f.1-8-97) 8. Two Awards of Rs. 100/- each to officers giving in Hindi in various Railway offices (w.e.f.1-4-98) 6. Translate into Hindi. (i) Memorandum ii) Service Register (iii)Confidential Report (iv)Please speak (v) Widow complimentary pass (vi) Urgency (vii) Increment (viii)Scale of pay (ix) Industrial Relations (x) Seniority List (xi) Honorarium (xii) Gazette Notification (xiii) Fixation of Pay (xiv) Official Language (xv) Nominee
(xvii) Notification
(xviii)Oath of Allegiance
(xix) Personnel Department
(xx) Periodical Medical Examinatio
The refrigeration system consists of 4 basic major components and refrigerant. Compressor, Condenser, Expansion device and evaporator. The refrigerant system depends for its action on latent heat principle and expansion principle.
The refrigerant in gas form is sucked into the suction side of the compressor and compressed to high pressure. From the compressor, the gas goes through a condenser which removes the sensible heat generate in the gas due to compression as well as, the latent heat and the gas liquefies. The liquid gas passing through an expansion valve into the evaporator is expanded to gas absorbing the latent heat in the process, thus cooling the cooling coil. The gas having taken up its latent heat in properly designed cooling coil is now dry and is again sucked into the compressor to continue on another cycle.
REFRIGERATION CYCLE
- Absorption of heat by the evaporation of a liquid refrigerant in the evaporator at a controlled lower pressure.
- Raising the pressure of the low pressure vapour coming from the evaporator by the use of the compressor.
- Removal of heat from the high vapour in the condenser so as to liquidity or condense the vapour and
- By the use of the throttling device, reducing the pressure of high pressure liquid (from the condenser) to the level of pressure needed in the evaporator.
7. List out Refrigeration tools? Flaring tool, crimping tool, tube bender, pinching tool, swedging tool, for pipe, charging line, pipe wrench, adjustable spanner and spanner set.
8. List out types of AC Coaches?
a) Under slung Conventional AC Coaches and roof mounted package unit fitted AC Coaches. AC First class, AC II tier, AC III tier, AC Composite, AC Chair cars.
9. List out parts of Under Slung AC coach? Compressor, Compressor motor, condenser, condenser fan motors, liquid receiver, dehydrator cum filter, thermostatic expansion valve, evaporator, blower motor, fresh air filter, return air filter, 18 KW Alternator, Rectifier cum regulating unit, 800 AH battery, pre-cooling transformerrectifier unit.
10. What are the parts of electronic thermostat used in RMPU AC coaches?
A) The electronic controller
B) Remote sensor
11. What are temperature setting recommended by RDSO in case of electronic thermostat?
As per the RDSO recommendations the temperature in the coach should be with electronic thermostat
Plant cut in temperature in summer - 25°C
Plant cut out temperature in summer - 23°C
Plant cut in temperature in winter - 19°C
Plant cut out temperature in summer - 21°C 5
12. Explain about Electronic thermostat used in AC coaches?
The unit is intended to provide ON/OFF control of the refrigeration plant/heater by sensing the temperature of the air at the return air grill.
The unit except the sensor shall be mounted in AC control panel, which is in the non-air conditioned space, and the sensor shall be mounted at the return air grill of the air conditioned space. The unit shall be designed for continuous operation. The unit shall give output signals through the contacts of the relays at the final stage of it to switch on either the heating control circuit or the cooling (refrigeration plant) control circuit. The operating point of the relay corresponds to the heater shall be capable of being selected between 17 & 21 deg. C. The operating point of the relay corresponds to the refrigeration plant shall be capable of being selected between 22 & 26 deg. C. The desired settings for the heating and cooling shall be obtainable in the following steps. The temperature setting are given in deg. C
Cooling Heating
Medium - 25 19
High - 23 21
The drift on the selected settings (due to variation in ambient temperature, input voltage fluctuations, ageing of the components and error on account of any other reason) shall not be more than +/- 0.2 deg. C. The differential between the cut-in and cut-out operation of the Heater/Refrigeration plant shall be between 0.5 deg. C minimum and 1.0 deg. C maximum.
At final stage of the unit there shall be two relays one for the heating control circuit to switch on the heater through its contactor and the other for the cooling circuit to switch on the refrigeration plant through its contractor. Each relay shall have one N/O and one N/C contact. The relay used for heater circuit shall get energized when the temperature at the sensor is less than the set value for heating and the relay that used for refrigeration plant shall get energize when the temperature at the sensor is more than the set value for cooling. The contacts of these relays shall be rated for and inductive load of 3 amp at 110V ac PWM power supply.
The unit shall be capable to work from 110V ac +/- 10% PWM supply with maximum ripple content of 15%. The design shall take care of the series connections and the surges that may be present due to switching ON/OFF of these loads controller shall be design in such a manner so that relay operation is chattering free.
The unit shall be provided with reverse polarity protection against inadvertent wrong connections of the polarity of the power supply.
The unit shall be designed to take care of an over voltage of 200V for one minute at the power supply terminals.
13. List out parts of RMPU AC coach? Hermetically sealed compressor, condenser, condenser fan motor, capillary tube, Accumulator, Evaporator, Blower motor, Fresh air and Return air filters, 25 KW Alternator, Rectifier- Regulator units, 1100 AH battery, pre-cooling rectifier units, 25 KVA inverters.
14. Compare between RMPU and Under slung AC unit? Comparison of Roof Mounted Ac,
15. List out types of WRA? WRA with DC Motor and compressor WRA with AC Motor and compressor 3-phase self priming mono block pumps.
16. How many types of gauges used in AC coach? Pressure gauge, compound gauge, LP gauge, HP gauge, and oil pressure gauge.
17. What are the operating Pressures of Under Slung AC coaches? LP = 37 to 46 psi HP = 150 to 180 psi OP = 70 to 90 psi
18. Draw the tube light circuit diagram?
19. What is the function of AC compressor? Compressor: It has two fold functions. It removes Vapor from the evaporator at a rate, which will permit steady state conditions of temperature and pressure in the evaporator. It discharges the Vapour at a pressure and temperature high enough to permit heat rejection along a descending temperature gradient to the cooling water or air of the condenser
20. Rating of the fuse used for phase supply & field supply in Regulator of AC Coaches. Phase supply fuse for 25KW Regulator – 160 Amperes. Field supply fuse for 25KW Regulator – 6 Amperes.
21. What is the capacity of cells used in AC Coaches? 800AH in under slung conventional AC coaches and 1100AH in RMPU AC coaches.
22. Action to be taken if Compressor Short Cycles.
23. Action to be taken if compressor runs continuously.
12.1.3 Compressor Runs Continuously
High discharge
a) Discharge shut off valves not fully opened.
b) Air or non condensable gas in the system.
c) The condenser pipes are blocked by mud or scales.
d) Too much refrigerant in the system. Open valve. Purge the foul gas from the condenser. Clean the condenser pipes. Drain off the refrigerant into the empty cylinder.
24. Reason for low suction pressure. Sr. No Trouble Possible Causes Suggested remedies 1 Low suction pressure
25. Give reason for less cooling and remedies. Inadequate Cooling
- Check thermostats. If mercury column has broken, replace it by a new one from the spare. If spare is not available, move the control switch(46), in any other position (Low, Medium or High) as may be the case.
- Check whether accelerating contactors (13 & 13a) in the case of old AC control panel have made contacts. If they are not closed, adjust the motor control relay (23) such that the above contactors get close.
- Check High pressure gauge reading. If the HP reading is more than 180 psi, open the wheel valve located in the cubicle for a short while for admitting water for cooling the condenser 10 tubes and fins and close the valve after HP reading indicates 150 psi. This operation has to be repeated whenever the HP shoots up to 180 psi.
- Check the condition of the blown fuses, replace the fuses of the corresponding circuit. If the fuse fails again, do not replace again, but note down in the log sheet for further action at the base station.
26. Describe procedure for replacement of Maneurope Compressor. Procedure for replacement of Compressor:
- Braze a 1/4” (6 mm) OD copper tube fitted with shut off valve at one of the ends. Connect the shut off valve through a charging line to an empty refrigerant cylinder and keep in a cold iced water container until all gas is extracted. Weight the cylinder before and after. Ensure that weight gain is minimum 2600 grams. A gas compressor can also be used to extract the gas and forcing it into the empty cylinder.
- Unsolder the suction and discharge lines and disconnect the electrical wiring from the compressor.
- Remove the compressor and clean the cylinder using carbon tetrachloride (CTC) with the help of circulating pump. It is advised that CTC flushing should not be done with compressor in circuit.
- Install a new compressor, and resolder the suction and discharge lines. Make the electrical connections. Use high quality silver based copper solder with minimum 40% silver.
- Test for leakage under 30 kg.cm2 pressure using Nitrogen/Carbon dioxide gas cylinder fitted with a two stage pressure regulator.
- Create a vacuum of 50 micron for 15 minutes with the help of two stage rotary vacuum pump to extract the moisture from inside of the refrigeration system.
- Charge the quantity of refrigerant gas (R 22) as per recommendation of the manufacturer. Charging slub-tube on the compressor should be 1/4” OD and of heavy gauge. Pinch off charging tube nearest to the compressor body so that it remains as short as possible. Longer stub tube can break due to vibrations. Place slight amount of solder at the pinch point for strengthening.
Leak Test:
Disconnect the low pressure cut-out and pressure-charge the system with dry nitrogen at 24 kg/cm2 (350 psig) and check for leakage with soap solution.
Evacuation :
After leak test, connect the system on both the low & high side to a vacuum pump for at least 4 hours and pull up to 200 microns (29.9 inch Mercury Column) of vacuum. Use electronic or tube type gauge, for checking vacuum.
Charging:
Now charge the system with 2.85 kg R-22 gas. This can be done by pulling a vacuum on a 5 kg gas cylinder and charging it with 2.85 kg R-22 gas by weight. (Weight the cylinder before and after filling gas. The difference should be 2.85 kg in weight). Check with halogen leak detector after charging the system.
28. What is the normal current drawn by RMPU AC plant?
Normal currents for various equipment are as under:
Package in cooling : 10 - 21 Amps (SIDWAL) mode 18 - 20 Amps.(Feeders)
Compressor motor : 7.5 to 9.0 Amps.
Condenser motor : 1- 1.5 Amp (Feeders)
each 1.8- 2.3 Amp(SIDWAL) each Blower motor : 2.0 - 2.3 Amp.
Each Heaters : 8 Amps. each.
29. AC Plant not working in auto mode.
What action you are going to take. Check for the proper working of PCB and Thermostats.
Keep the package in the auto mode. Run the blower. Short points 3 and 4 PCB. The compressor should come 'ON'.
Open the points 5 and 6 heater should come on. Operate the machine manually in case of thermostat failure or PCB failure.
Shift Rotary - Switch RSW-4 from "AUTO' to "COOL-ING or I-EATING manual mode.
The AC Unit will now operate continuously thus by-passing the Thermostat. During manual operation thermostat goes out of the control circuit and machine will run continuously in the selected mode of operation.
In case of excessive cooling, the compressor will switch off from low pressure cut-out and in case of excessive heating, the heater will switch off from the safety thermostat. The ACCI should switch ON /OFF the plants by monitoring the temperature inside the coach with a thermometer.
30. What is Cut in & Cut of pressure of WRA Cut out
CUT IN --- 0.3 Kg/sq.cm
CUT OUT -- 0.7 Kg/sq.cm
31. What are major differences in equipment and operation of Air conditioning system under slung and RMPU equipped coaches.
32. What are the AC system presently being used in our Railways and mention the feature of each type and where they are used. Two types of AC system are being used Viz., RMPU fitted AC Coaches and Under slung conventional AC Coaches. Both these coaches employed Vapour compression system for refrigeration. RMPU:
1) This is hermitically sealed system with no fittings or openings and used 3-phase AC Motors. Hence less maintenance
2) Uses Refrifirent R-22 apply 3 kgs.
3) The package is mounted on the roof thus dirt or dust collection in condensers negligible, No chance of damage due to the flash floods, cattle run or flying ballast.
UNDERSLUNG: The compressor used is open type which can be easily be attended in case of repairs. The compressor moor and compressor are both separate units. Defective motor will not have any effect on the compressor. The system is easy to understand because of provision of pressure gauges. The refrigerant used is R12 approximately 15 kgs.
33. What are the refrigerants generally used in Air conditioning system. What are the required properties of refrigerant?
Refrigerant – 12 and 22 are used in under slung conventional AC Coaches. And RMPU AC Coaches respectively.
13 Recently Railways has introduced use of R-134 A environment friendly refrigerant and some of the RMPU coaches have been converted into R-134 A refrigerant.
REQUIRED PROPERTIES:
1) The refrigerant shall be non poisonous, non inflammable, non corrosive and non irritating.
2) It shall have no harmful effect on the taste, colour or Aroma of food and drinking water.
3) It shall have low boiling point
4) It shall have high latent heat of vaporization
5) It shall have low volume per kg. When in gaseous state
6) It shall have high coefficient of performance
7) Easy detection of refrigerant leakage
8) It shall be cheap and readily available in the market.
34. What are the essentialities of coach Air conditioning?
The essentialities are -- The working of blower fan of the evaporator and the blower fan of the condenser has to be ensured before the compressor starts functioning
-- Suitable protection to ensure proper lubrication of the compressor to avoid piston seizure.
-- The excessive pressure on the discharge side of the compressor should be avoided
-- The suction pressure should not be lower than specified to prevent frosting of the evaporator and liquid entry into the compressor
-- All the motors should not be switched at a time to prevent sudden inrush of starting current.
-- A suitable interlock has to be provided to ensure that heater is not on, when compressor is working.
-- Low voltage protection is required in order to avoid undue drain on battery
-- The blower fan has to come ON before the heater compressor ON.
-- Over load protection and short circuit protection for all electrical circuits.
35. What are the different types of AC coaches presently in use, explain theca system in coach in brief. Two types of AC system are being used Viz., RMPU fitted AC Coaches and Under slung conventional AC Coaches. Both these coaches employed Vapour compression system for refrigeration.
RMPU:
1) This is hermitically sealed system with no fittings or openings and used 3-phase AC Motors. Hence less maintenance
2) Uses Refrigerant R-22 apply 3 kgs.
3) The package is mounted on the roof thus dirt or dust collection in condensers negligible, No chance of damage due to the flash floods, cattle run or flying ballast. UNDERSLUNG: The compressor used is open type which can be easily be attended in case of repairs. The compressor moor and compressor are both separate units. Defective motor 14 will not have any effect on the compressor. The system is easy to understand because of provision of pressure gauges.
The refrigerant used is R12 approximately 15 kgs. Also
1. Self generating AC coaches: - In these AC coaches each coach is equipped with its own generating equipment like 3-phase Alternator and a set of battery to cater to the requirement of total electrical load of the coach. It is also equipped with a Pre-cooling transformerRectifier unit for taking shore supply.
2. End on generation AC coaches: - In trains like Rajdhani express & Shatabdi express the coaches depend on the power supply from Power cars. The rake of the train is provided with a power car having two nos of Diesel generators, one will be working and the other is standby. This power car is placed at the end of the rake formation. The supply is fed to all the AC coaches with the help of inter vehicle couplers. 36. Write short notes on the following:
a) Refrigerator Refrigerators operates on the Vapour compression system having hermitically sealed compressor mounted at the base of the cabinet. Refrigerant used is R-22 or 134
A. Expansion valve used is capillary tube. The evaporator piping is fastened round and brazed to the freezer box. The condenser tube is placed over a single metal sheet for dissipation of heat. The top space is freezer unit. and the rest of the cabinet interior gets cooled by convection currents of air set up by freezer unit.
b) Water cooler: - Water cooler is a machine working on refrigeration system for cooling water for drinking purpose. The refrigeration system is same which is utilized in airconditioning, refrigerators, etc. Generally two types of water coolers are used i.e., Instantaneous water coolers and storage type water coolers. In addition to the above two types there are also storage-cum-instantaneous type also. The drinking water having temperature between 10 degree C to 13 degree C is preferred.
c) Window type AC units: - These are completely self contained units, with the compressor, condenser, evaporator, refrigerant piping and air filter, all assembled in a very compact assembly. The window units are usually of ½ to 2 tons capacity and fitted with 230 volts motor. The refrigerant is controlled with the capillary system. The unit is so designed that it can be mounted on the window with small bracket from outside.
d) Air filter in ac system: Air filters are used to maintain cleanliness / dustproof. There are mainly two types of air filters. Viz., Return air filter is to remove any dust present in AC room/Coach and fresh air filter is used to filter fresh air for dust etc.,
e) Evaporator in refrigerator system: This constitutes the cooling unit, in which the liquid refrigerant under low pressure evaporates and in doing so, it takes away its quota of latent heat, there by cooling the medium surrounding the cooling coil.
f) Dry and Wet bulb temperature: Dry bulb temperature is the temperature of air as measured by an ordinary thermometer. 15 Wet bulb temperature is the temperature of air as measured by an ordinary thermometer, whose glass bulb is covered by a thin cotton sleeve soaked in water.
g) Condenser: It is intended for cooling the hot gas and liquefying it under pressure. It may be air cooled or water cooled
h) Sealed compressor of AC unit: The motor and the compressor unit is housed in one casing and completely sealed. The suction and discharge piping is brazed as no valves are used , the chances of leakage is eliminated.
37. What is difference between dry bulb and Wet bulb? Dry bulb is the temperature of air as measured by an ordinary thermometer whereas wet bulb temperature is the temperature measured by an ordinary thermometer, whose glass bulb is covered by a thin cotton sleeve soaked in water.
38. What is difference between humidity and relative humidity?
Humidity is the amount of water vapour present in the air whereas Relative Humidity is the ratio of the actual amount of water vapour contained to the maximum amount required for saturation and is expressed as a percentage.
39. What is meant by due point?
It is the temperature of air at which the moisture present in air starts condensing.
40. What will happen if the AC plant capacity is insufficient for load?
If the AC plant is insufficient for the load the desired temperature will not be attained in the room. The AC plant will run continuously under vapor pressure rises considerably overloading the compressor. The condensation of the refrigir3nt will not takes place in the condenser.
41. How is any leak of the refrigerant detected in refrigerating circuit. When the LP and HP pressures are persistently low and cooling is insufficient, frosting of evaporator, it shows less gas in the system giving indication that there is leakage of refrigerant from the system. Leakages can be detected by conducting low pressure test on suction side and high pressure test on discharge side of the system.
42. How do you attend to a leak joint?
Soap water is applied on the piping and equipments. If any leakage is there, bubbles will form on the soap fomentation. That place is to be brazed / repaired.
43. What is the procedure for final testing and commissioning of a new AC plant Package system?
- Visual inspection of the coach proper fitment of equipments
- Ensure the refrigerant pipes are properly clamped
- Suction pipe for proper lagging
- Check control panel and ensure that proper fuses are provided
- Check contactors, relay and switches for correct sequential operations
- Ensure the time delay in operation of contactors feeding compressors
- Check heaters for correct operation
- Check hooter for roper operation
- Start the plant and check condenser motor, compressor motor, blower moor for any abnormalities
- Check the current drawn by the motors and compare with its rated current.
As per the RDSO code of practice RDSO/PE/O/0008-2005 REV.O the following are the measures to be adopted for prevention of fires on AC coaches:
i. The air-conditioned coaches are to be provided with elastomeric copper cables if the size is more than 10 sq.mm. in case of old coaches.
ii. The air-conditioned coaches are to be provided with PVC cooper cables if the size is less than 10 sq.mm. in case of old coaches
iii. For new AC coaches E-Beam irradiated thin walled elastomeric cables are to be used. iv. The number of joints and junction boxes should be minimum.
v. Correct size of cables is to be provided for different circuits as per load.
vi. All the cables other than branch cables shall be secured to the coach structure by cleats located at an interval not exceeding 500 mm.
vii. All the cables other than branch cables either side of bend and near all end connections, extra cleats are to be provided not exceed a distance of 150 mm.
viii. The edges of the groove for holding the cables in the two halves of the cleat shall be suitably chamfered to avoid pinching of cable insulation.
ix. Branch cables are to be secured by PVC insulated clips. These clips shall be attached to the coach body by screws.
x. PVC/FRP Cleats with non-inflammable properties only shall be used.
xi. Wherever cables pass through holes, orifices, slits, apertures etc. with sharp metal edges, such opening shall be provided with fire retardant PVC grommets grade 6.
xii. The cables should be terminated in the junction boxes, terminal boards etc. with lugs.
xiii. The cables should be not have any intermediate joints and should be terminated in junction boxes, terminal boards.
xiv. Laptop/mobile charging points should not be used for Radio, electric shaver or any other appliances.
xv. Locking and securing arrangement for the doors and covers of electrical control/power cubicle and terminal boards should be ensured to prevent unauthorized access to the live parts of electrical equipment.
xvi. There should not be earth leakage one either positive or negative cables.
xvii. All the electrical fittings both on super structure and on under fame shall be mounted directly on the coach body and shall not be electrically insulated.
xviii. All the electrical equipments above 110V shall be individually provided with earthing shunts between equipment body and coach body.
xix. The clearance between live part and coach body should be 10 mm and 4 mm between parts of opposite polarities for 110V system.
xx. The insulating fire retardant low-tension (FRLT) tape should only be used in the coaches. xxi. Coaches, poor joints should not be allowed.
xxii. The IR value should not be less than 2 mega ohms for 110V, 190V, 230V when measured with 500V megger and 3 mega ohms for 415V circuits when measured with 1000V megger.
xxiii. The rewiring of coach should be done after 12 years. However it should not exceed 15 years even if the wiring is good.
xxiv. The battery boxes with LMLA batteries shall be provided with FRP trays at the bottom of the battery box to avoid corrosion of battery box due to spilling of acid. The box shall be provided with ventilating grills and drain pipe to permit the flow of outside air over the cells and to allow spilled acid and water to drain out.
xxv. The battery box shall have minimum 150 mm clearance at the top of the battery for maintenance of cells.
xxvi. The battery box should be painted with two coats of acid resistance paint to protect against corrosion from battery acid.
xxvii. Correct size of fuses and MCBs to be maintained to blow/trip in case of abnormality
xxviii. It should be ensured that the vane relay should work properly. xxix. It should be ensured that the OVP should work properly.
xxx. Fans, berth lights, step lights, tail lights, and side light fittings to be provided with connecters for feeding supply to them.
xxxi. Connectors used in should be made of tough non-ignitable moulding material or rigid PVC.
45. Describe briefly the equipment used in Railway air conditioning coaches.
Compressor:
It has two fold functions. It removes Vapour from the evaporator at a rate, which will permit steady state conditions of temperature and pressure in the evaporator. It discharges the Vapour at a pressure and temperature high enough to permit heat rejection along a descending temperature gradient to the cooling water or air of the condenser
Condenser: It is intended for cooling the hot gas and liquefying under pressure. It may be air cooled or water cooled.
Expansion valve:Is function is to control and regulate the rate of flow of the liquid refrigerant under high pressure and allow it into the evaporator under low pressure.
Evaporator: This constitutes the cooling unit, in which the liquid refrigerant under low pressure evaporates and in doing so, it takes its quota of latent heat, there by cooling the medium surrounding the cooling coil.
Alternator:25 KW alternators are used for RMPU coaches and 18 KW for under slung coaches. These are brushless alternators generates 3-phase AC supply Rectifier regulator unit: His is used to rectify Ac out put of the alternator to DC supply It provides DC supply to the field of the alternator. The DC output voltage and current is maintained within set limits by regulating the DC supply to the field.
Battery:
- For RMPU coach 56 no.s of VRLA cells of 1100 Ah are provided and 56 no.s of 800 AHR lead acid cells are used for Under slung coaches. Maintenance depots should be check and adjust the tension during the first 3 consecutive trips and every 2 months thereafter. Too much tension, shortens belt life and also bearing life. Too little tension allows belt to sli0 and generate heat thereby reducing life. Check alternator and axle pulley grooves with limit gauge or template after every 3 months. Worn-out side-wall or sharp objects on the grooves may result in short life of V belts. Replace the full set of old belts with new belts of same make, grade and batch,
- Check condition of bearings, improper bearings may lead to heat generation which would reduce the belt life.
- Store belts in a cool, dry, well ventilated place away from sunlight or any other sources of heat, oils, greases or corrosive fumes.
- V belts may be hung loosely or laid flat but should never be squeezed into respective spaces. Belts shall not be kept in a heavily bent or piled condition.
- Avoid wherever possible, tying V belts tightly with string.
- Use belts within 2 years from the date of manufacturing, as age and storage condition may alter the belt length. In case of bulk procurement, deliveries can be staggered in quarterly installments.
46. Explain working principle of KEL ALTERNATOR/REGULATORS 25KW 135V with the help of circuit diagram?
Ans. For easy understanding of KEL 25 KW alternator/rectifier regulator circuit diagram, was divided into five sub circuits. They are
1. Power supply circuit
2. Field circuit
3. Voltage control circuit
4. Current control circuit
5. Over voltage Protection Circuit
1. Power supply circuit:
This circuit consists of 3 phase alternator(ALT) fuse F1,3 phase bridge rectifier.(PR). Capacitor bank (C1,C2,C3) and current transformers (CTI to CT3). Three phase AC supply (13,14,15 terminals UVW) produced by alternator is fed to 3 phase bridge rectifier through fuse F1. The bridge is protected against voltage surges by 6 numbers of 0.25 mfd 600V capacitors (C1). One 10 mfd 250V capacitors (C2) and one 10 kpf 500V capacitor (C3) are provided across the bridge for filtering DC output and protection against high frequency surges respectively. Capacitors, C, c and resistors are provided as filter for reducing the ripple content. Three current transformers primaries are connected in series to the alternator supply.
Function: When the field coils are excited and rotor is rotated the variation in reluctance offered by the rotor teeth arrangement causes the flux produced by the field coil to pulsate. This pulsation of flux linked with Ac coils and induces e.m.f in the AC windings. The induced e.m.f. in the 3 phase winding is rectified by the 3 phase bridge rectifier. The bridge rectifier also serves the purpose of maintaining the constant polarity in both the directions of the train and prevents current flowing from battery to alternator, when the coach is stable condition.
2. Field circuit:
Field circuit consists of Magnetic amplifiers (MAI & MA1), field full wave bridge rectifier (D1,D2,D3,D4) and free wheeling diode (D5) and normally closed contact of relay. ET is eliminated and Two Magnetic Amplifier are used to control the field voltage and field current, there by controlling the output voltage and output current. MA has six windings. Two are load windings connected in series to the field circuit. One winding is used for voltage/current control and one more winding used as feed back (gain) winding to boost output voltage whentrain is in slow speeds. Two winding are spare. Free wheeling diode is provided to eliminate the surge voltages produced in the field coil. Cathode of free wheeling diode connected to field positive and anode to field negative.
Two phase AC supply of Alternator given to bridge rectifier through field fuse F2, NC of CR, MA1, and MA2 load windings. Load winding terminals are arranged in such way that, series connected two windings of MA1 and MA2 are included in each half cycle. Load windings 162,17, and 162, 17 are connected in one half cycle and 161,18 and 161,18 are included in the other half cycle. The rectified DC positive is fed to field positive (+EX) of alternator through gain winding 40 and 20 Two gain windings of MA1 and MA2 are connected in series. Rectifier negative (19) of bridge rectifier is connected to field negative (-EX). Freewheeling diode is connected across field terminals (19 and 20) in reverse direction. Function: The purpose of field circuit is to feed rectified DC supply for field for excitation. Two phase supply of alternator is rectified by bridge rectifier. This rectified DC is fed to field winding through gain winding. Free wheeling diode is provided to dissipate energy produced in the field, in other way to eliminate surge voltages produced in the field coil. Load windings are connected in the field circuit to vary the field voltage and current.
3. Voltage control circuit:
This circuit consists of auxiliary rectifier (RT1) voltage detector (DT1) and voltage control winding of magnetic amplifier (10,11) blocking diode(D6). The voltage detector consists of resistance network (R1,R2,R3,).and zener diode D8, potentiometer (RH1) is connected across the resistance R3 to vary the output voltage settings. Voltage detector serves the purpose of providing DC signal to the control winding of MA. Function: When the output voltage exceeds the preset value, the drop across R1 is sufficient to conduct zener diode and allows a DC signal to the voltage control winding of MA.
The DC flux produced in control winding will oppose the AC flux of load winding and increases impedance of the field circuit. This increase of impedance, results in decrease of field voltage and field current 20 thereby decreasing output voltage. This process is continuous to maintain the output voltage constant. The voltage setting can be varied by varying the potentiometer. In ’25 KW KEL RR unit the control winding (10,11) are common for both voltage and current control. Two control windings of MA1 and MA2 are connected in series. Diode D1 is provided to prevent creep age of current from DT2 to DT1
4. Current control circuit:
This circuit consists of 3 phase bridge rectifier (RT2), current detector (DT2), blocking diode (D7), control winding of MA(10 & 11), and secondary o f current transformer (CT1 to CT3) The CT1 to CT3 play important role in the current control circuit. The primary of the CTs connected in series with the 3 phase AC supply. The secondary of CTs connected to 3 phase bridge rectifier (RT2). The output voltage of RT2 connected to current detector. RB1 connected across DC output which acts as burden resistance. Current detector consists of resistance network R4,R5 and R6 and zener diode D9. Zener diode D9 is connected across R4 is in series with blocking diode D7 and control winding of magnetic amplifier (10-11). D2 prevents current from DT1 to Dt2, RH2 is provided across R6 to vary the current settings. Function: The current transformer CT1, CT2 and CT3 senses the current flowing in the 3 phases. The burden resistance RB1 converts current signal into voltage signal. This Dc voltage is fed to voltage detector. The voltage obtained from the secondary of CTs fed to the 3 phase bridge rectifier RT2. When the current delivered by the alternator reaches predetermined value the voltage drop across R4 is sufficient to conduct the Zener diode, thereby sending the control current to magnetic amplifier control winding and increases the impedance of field circuit, thereby decreasing field current/output current. This is a continuous process and maintains output current at present value.
5. OVP Circuit:
It consists of auxiliary rectifier (D13, D14, D15) Zener diodes (Z1-Z2), potentio meter(pot) transistors (T1,T2,T3), relay coil (CR), freewheeling diode (D12) and LED (D18). Function: When the output voltage shoots up more than 150 Volts due to failure in control circuit, the drop across middle terminal of potentiometer and negative will be more than Zener voltage of Z2, zener diode Z2 transistors TR1, TR2, TR3 conducts. The relay energized through R4 and TR3, and field supply through NO (Normally open) of relay coil. At this stage the relay is permanently energized unit the reset push button is pressed at base station by staff. Hence, once, over voltage occurs, the field is permanently cut off in this type of regulators. D12 is provided across relay coil to dissipate energy stored in it. Z1 is reference voltage diode. Glowing D17 indicates normal working. CELLS
47. Explain working principle of cells?
Working Principal of Cells: PbO2+Pb+2HSO4↔2PbSO4+2H2O Discharging PbO2 on (+ve) plate and Pb on (-)ve plates are converted into lead sulphate. In this process, HSO is converted and water is formed. Consequently SPG of electrolyte falls and extents of fall is proportional to Ah taken out. Charging: The chemical process is reversed. PbSO4 on positive plate is converted into PbO2 (lead peroxide) and PbSo4 on negative plate into Pb ( spongy lead ).H2SO4 is formed and water is consumed.SPG of electrolyte rose.
48. What are the types of Batteries used in Indian Railways? Types of Batteries used in Indian Railway:
A. Lead Acid:
1. Conventional type
2. VRLA (Valve Regulated Lead Acid Batteries )
3. Low maintenance Batteries
B. Alkaline Batteries:
1. Nickel Cadmium
2. Silver Zinc Constructional features:
1. Positive Plates
2. Negative Plates
3. Separators
4. Container
5. Cell cover Accessories:
a. Float
b. Float guide
c. Vent Plug Capacities of Batteries In train Lighting:
A.120 Ah-110 v DC, BG, TL coach
B.800 Ah-110 v DC, BG, ACCW AC coach
C.1100 Ah (VRLA)-110 v DC, BG, convention type AC coach
D.120 Ah (VRLA)-110 v DC, BG, TL coach
E.1100 AH (Low maintenance)-110 v DC, RMPU type AC coach.
49. Explain Initial Charging to a new commissioned battery in workshop?
Initial Charging to a new commissioned battery:
Lead Acid Batteries are supplied in uncharged condition without electrolyte. Before using Lead Acid battery, it has to be initially filled with recommended quality and quantity of electrolyte and make ready for initial charging. The whole phenomenon is associated with the following activities:
a. Preparation of Electrolyte
b. Initial filling
c. Initial charging Preparation of Electrolyte:
- The cells are supplied in dry uncharged condition.
- These cells are required dilute Sulphuric acid of SPG ( 1.108-1.22), corrected up to 27 degree Centigrade as electrolyte for initial charging.
- Electrolyte =H2SO4 ( as per IS:266) of SPG 1.835+ Water ( as per IS:1069) To get 100 litres (approx) of electrolyte: For SPG Water (litres) Acid (litres) 1.180 86 17 1.220 82 21 Concentrated acid should always be poured into the water and never the water in the acid in Ebonite box.
Initial filling:
- Filling the electrolyte up to the lower marking on the float indicator
- Allow the cell to rest for a period of around 16-24 hrs.
- Level of electrolyte may fall. Restore this with some electrolyte.
- Now the cells are ready for 1st charging. Initial Charging:
- Charge the cells for 80/100 hrs at specified rate as per manufacture’s data . (40 A for 800 Ah, 06 A for 120 Ah…….)
- During charging, temperature should be less than 50 degree. After 45 degree, reduce the charging rate to ½ value & increase the time accordingly.
- Total charge input should be equal to Time X current ( specified Charging current )
- While charging, level of electrolyte may fall due to water loss. Restore for 24 hrs by adding water. Adjust the SPG to 1.215+/-0.005 corrected to 27 degree.
- Adjust the SPG, the cells must be gassing freely for a minimum 2 hrs of charging. This helps in proper mixing of electrolyte.
- Now cells should be discharged through a suitable resistance at constant current (I)=0.10XC10 amps up to 1.80 VPC.
- The battery shall be charged at normal charging
50. Explain Trickle Charging of Batteries?
Trickle Charging: When a battery is kept as an emergency reserve, it is very essential that it should be found fully charged when an emergency arises. Due to leakage action and open circuit losses, the batteries deteriorate .Hence to keep it fresh, batteries are kept on a small charging.
For example: A standby battery for station bas-bar of 400 Ah at 10 hr rating, a continuous trickle charge of 1 Amp will keep the cells fully charged and keep in perfect condition.
51. What are the Indications of a fully charged cell?
Indications of a fully charged cell: The indications of a fully charged cell are:
(i) Gassing
(ii) Voltage
(iii) Specific gravity and colour of the plates
(i) Gassing When the cell is fully charged, it freely gives off hydrogen at cathode and oxygen at the anode, the process being known as “Gassing”. Gassing at both plates indicates that the current is no longer doing any useful work and hence should be stopped. Moreover, when the cell is fully charged, the electrolyte assumes a milky appearance.
(ii) Voltage The voltage ceases to rise when the cell becomes fully – charged. The value of the voltage of a fully – charged cell is a variable quantity being affected by the rate of charging, the temperature and specific gravity of the electrolyte etc. The approximate value of the e.m.f is 2.1 V or so.
(iii) Specific Gravity of the Electrolyte A third indication of the state of charge of a battery is given by the specific gravity of the electrolyte. We have seen from the chemical equations of Art.9.9, that during discharging, the density of electrolyte decreases due to other production of water, whereas it increases during charging due to the absorption of water. The value of density when the cell is fully charged is 1.21 and 1.18 when discharged up to 1.8 V. Specific gravity can be measured with a suitable hydrometer which consists of a float, a chamber for the electrolyte and a squeeze bulb.
(iv) Colour The colour plates, on full charge is deep chocolate brown for positive plate and clear slate gray for negative plate and the cell looks quite brisk and alive.
52. What are the Factors affecting the life of Lead Acid Battery?
Factors affecting the life of Lead Acid Battery:
1. Necessity of frequent topping of cells.
2. Leakage of electrolyte on lid and on container body.
3. Failure on one cell on a mono-block unit.
4. Undercharging / overcharging.
5. Always use distilled water for toping of cells.
6. Keeping the discharged cells for long time will result in formation of sulphation.
53. What are the diseases associated with a Lead Acid Batteries and their remedial action?
DISEASE CAUSING TO LEAD ACID BATTERIES OF TL CELLS The diseases are:
1. Sulphation
2. Bucking and cracked plates
3. Loss of capacity
4. Low specific gravity and low voltage of cell
5. Reversed cells 6. Dead cells
7. Loss of active material
8. Sludge
9. Internal short circuit of one or more cells.
SULPHATION: Sulphation means the formation of lead sulphate on the surface and in the pores of the active materials of the plates. Sulphate is finely crystalline and easily reduced by the charging current. Sulphation in this sense is a necessary part of the operation of battery and is not a source of trouble. Lead sulphate is also formed as result of local action or self discharge of the plate. This is brought about by the action of the acid solution on the concentration and temperature of the electrolyte. Lead sulphate formed as a result of local action is easily reduced by the charging current unless it is neglected. Sulphation applies to the large crystals of lead sulphate that may form on the plates as a result of neglect or misuse. Excessive sulphation of this type is difficult to reduce and may injure the plates. The effect is usually noticed by a whitish colour on plates and is caused by over charging, over discharging or keeping the discharged battery for a long time. Carbonate of soda added to the electrolyte has a beneficial effect in preventing sulpahtion defect, or the best way is trickling charge i.e., charging the battery at a low rate for long time.
CAUSES OF SULPHATION
1. Due to over charging
2. Over discharging
3. Impurities in acid, plates, or electrolyte
4. Due to plates are not covered by the electrolyte
5. Due to neglect of battery, Sulphation is caused
6. Kept under discharged condition for long time
TREATMENT FOR SULPHATED CELLS
Light sulphation:- If it is taken in time, charging at low rate approximately 1/3 rd of the normal charging rate will reduce sulphation. The charge should be continued till cells gas freely. Repeat charge and discharge two to three times till specific gravity of 1.220 is reached.
Badsulphation:- Empty the container and fill with distilled water, charge at 1/10th of normal rate and test specific gravity at intervals and it is above 1.150. Stop charging and empty out the electrolyte. Refill with pure distilled water and continue charge. Ensure that the temperature of the electrolyte does not rise above 120 degrees F (49 degrees C). The charge of the sulphate will be indicated by the colour of the plates. After all Sulphation is reduced empty the jar and refill with electrolyte of 1.220 Specific gravity. It is not advisable to use any de Sulphation agents since Sulphation is the natural result of battery action.
54. What are the points to be followed for the Healthy condition of the Battery set?
Maintenance of Lead – acid cells: The following important points should be kept in mind for keeping the battery in good condition:
1. Discharging should not be prolonged after the minimum value of the voltage for the particular rate of discharge is reached.
2. It should not be left in discharged condition for long.
3. The level of the electrolyte should always be 10 to 15 mm above the top of the plates which must not be left exposed to air. Evaporation of electrolyte should be made up by adding distilled water occasionally.
4. Since acid does not vaporize, none should be added.
5. Vent openings in the filling plug should be kept open to prevent gases formed within from building a high pressure.
6. The acid and corrosion on the battery top should be washed off with a cloth moistened with baking soda or ammonia and water.
7. The battery terminals and metal supports should be cleaned down to bare metal and covered with Vaseline or petroleum jelly.
HEALTHY CONDITION OF A CELL/BATTERY
Checking the SPGR of electrolyte. If it is 1.220 the battery are fully charged condition. If it is 1.175 half charged condition. If it is 1.100 it is in fully discharged condition.
1.Checking the voltage of the cell. Switch on lights and fans in coach before taking voltage. Reading as even a discharged cell may show 2volts on open circuit. Now measure the voltage of the cell. The voltage of the fully charged cell on discharge will be about 2volts. When the cell 25 voltage is about 1.85 volts, it should be considered as practically fully discharged and arrangements are made for charging.
55. Write short notes on Hydrometer and cell tester?
HYDRO METER: This meter is used to measure SPGR of liquids. It consists of glass tube with a glass bulb. The glass bulb is fitted with lead balls and is fitted with scale, on which SPGR is marked. This glass bulb is kept in a glass tube. One side of glass tube is fitted with rubber bulb and on the other side a nozzle. The rubber bulb is pressed to suck electrolyte from the battery. The electrolyte enters in the outer glass tube in which hydro meter bulb floats and gives reading. With the dilute sulphuric acid the bulb sinks more in the electrolyte, while with strong sulphuric acid the bulb less. In this way it gives reading to know the performance of battery.
CELL TESTER OR HIGH RATE TESTER
This is a tester which gives the correct terminal voltage on full load of the cell. In the tester there is one resistance of low value which works as load on the cell of the battery. One voltmeter is connected to give voltage. On the same voltmeter dial, charged to discharge conditions are also indicated by the words full charged, half charged and dead. One small lamp is connected in parallel with the voltmeter to indicate light. This tester gives the reading to one cell only at a time. Following precautions are to be taken while using this cell tester.
56. Explain the Salient features of VRLA batteries?
VRLA / SMF batteries The lead acid battery, used in the automobile industry, consists of a spongy lead negative and lead dioxide positive with sulphuric acid as electrolyte. It has a nominal voltage of 2V and requires periodic maintenance, depending on its use. The conventional lead acid battery is improved by developing valve regulated sealed lead-acid battery (VRSLAB) with absorbent glass mat or gel technology. These batteries need no addition of water during their normal life time. There is no spillage of electrolyte or release of gas. The batteries are charged by constant potential mode. Calcium alloys are used as grid material due to their lower self-discharges and increase conductivity. Oxygen and hydrogen evolve from positive and negative respectively during recharge. Oxygen evolved at the anode reacts with the hydrogen through the separator to produce water. A valve releases the excess gas, preventing accident during overcharging. VRSLAB finds usage in electronic equipment, standby systems and remote area power supplies where solar power is used to charge batteries.
57. What are the main parts of the VRLA batteries?
Parts of VRLA Batteries
1. Positive plates: Flat pasted type with lead-calcium High Tin alloy or lead cadmium alloy to resist corrosion & for longer life.
2. Negative plates: Flat pasted type with lead-calcium alloy grid for maintenance free characteristics. 3. Separator: Low resistance, high porosity and highly absorbent glass mat separator (AGM)
4. Electrolyte: High purity Sulphuric acid to maximize shelf life
5. Terminals: High conductivity lead plated inserts.
6. Safety Valve: Self resealing, pressure regulated and explosion proof.
7. Container and Cover Sealing: Heat Sealing Method (Fusion bond) for better joint strength 8. Container: High impact Polypropylene co-polymer
58. Explain Working principle of VRLA batteries?
Working principle of VRLA batteries Valve Regulated Lead Acid (VRLA) batteries can be of either the gelled electrolyte type or the absorbed electrolyte type, While the basic electrode reactions remain the same as in conventional flooded cells, VRLA batteries operate on the oxygen recombination principle. Due to the special grid alloys used, the actual gas evolution is 97% less than in conventional batteries. The conventional flooded batteries, oxygen evolved at the positive plate bubbles upwards through the electrolyte and is released through the vent plugs. In VRLA batteries, however, the small amount of oxygen that is evolved, is transported through the separator to the negative plate via the gas phase, and is consumed at the negative plate. Special features of VRLA batteries
FEATURES:
VRLA batteries using absorbed electrolyte have the following special features.
1. Starved electrolyte The electrolyte is immobilized by using highly absorbent glass mat separators which are designed to hold sufficient electrolyte to meet all performance requirements. Oxygen Recombination The battery works on the oxygen recombination principle. Recombination efficiencies are in excess of 99%. Explosion resistant safety vents VRLA batteries operate at a slight positive pressure within the cell. Cells are fitted with a unique low pressure self resealing safety vent plug which releases the gasses when the internal pressure within a cell exceeds 6 PSI and reseals again at low pressures. The constant positive pressure in the cells prevents accidental ingress of external air which would otherwise result in self discharge at the negative plate. The vent plugs are also fitted with a porous plastic disc, which prevent external sparks from entering the cell. This makes the vent plug explosion proof. Hermetic Heat Seal The battery jar & cover are hermetically sealed on automatic machines. Additionally, the total absorption of electrolyte in the separators and the use of pressure regulated vents make it spill proof and leak proof. Superior alloys VRLA batteries use highly corrosion resistant alloys such as Lead cadmium resistant lead alloys. Copper insert terminals VRLA batteries have highly conductive copper inserts in terminals resulting in very good power characteristics. Inter cell connections are done by using high purity lead coated copper strip connectors and heavy duty stainless steel bolts which are resistant to sulphuric acid. Modular Steel Trays VRLA batteries are assembled in modular steel trays normally in the horizontal configuration .This lends flexibility in assembling the system one module above the other.
59. What are the advantages of VRLA batteries over conventional flooded tubular batteries?
Advantages of VRLA batteries In Railway applications such as train lighting and air conditioning etc., VRLA batteries have marked advantages over the conventional flooded designs. Some of these advantages are given in the following comparison table: Conventional Flooded Batteries VRLA Batteries
1. Regular maintenance required involving topping up with distilled water.
2. A lot of excess free acid is available leading to acid stratification. This is more pronounced in taller cells. 3. There is a possibility of ground currents due to electrolyte spillage. This can result in high rates of self discharge.
4. Batteries are housed in MS boxes under the coaches.
5. There is a possibility of shedding of active material due to vibration in service.
6. These batteries are mounted vertically hence the ‘g’ force acting on the cell is high.
7. Post corrosion is usually observed due to the acid mist.
8. Cover sealed by bitumen to hard rubber container. Cracking and debonding of the sealing compound is a very common problem.
9. Self discharge rate up to 4% of capacity per week.
10. The average discharge voltage is 1.90VPC.
1. No periodic topping since this battery work on the oxygen recombination reaction resulting in zero loss of water.
2. No stratification of electrolyte because of the wicking action of the absorbent separators. The cells are mounted horizontally reducing the height of cell. Stratification is there fore eliminated.
3. There is no possibility of electrolyte spillage due to the dry leak proof construction hence ground currents are eliminated.
4. The VRLA battery unit can directly bolted horizontally to the under carriage of the coach. This will eliminates the need for battery boxes as well as the FRP trays used in existing designs.
5. Due to the highly compressible glass mat separators, the possibility of shedding of active materials is minimized. Hence VRLA batteries exhibit batter vibration resistance.
6. VRLA batteries are mounted horizontally reducing the ‘g’ force acting on the cells.
7. No post corrosion since there is no acid mist.
8.Cell covers and jars are hermetically heat sealed. No operational problems envisaged.
9. Very low self discharge of 0.5 to 1.0 % of capacity per week.
10. VRLA batteries have good voltage. The average discharge voltage is 1.95 VPC resulting in lower battery currents. There is therefore less heating and wear & tear of electrical components. The discharge plateau of VRLA batteries is also flatter
11. Transits damages are high because of brittle rubber containers.
12. Separate battery room and charging at site is required. This increases the time and space requirements for battery charging. leading to uniform intensity of light bulbs, for longer duration. 11. VRLA batteries are housed in steel trays which can withstand drops and shocks during transit. Hence transit damages are virtually eliminated.
12. These batteries are factory charged . Commissioning is immediate. A 80% savings installation time is quite common. Further , the requirements of a separate battery room and charger are considerably reduced.
60. Explain the procedure for the POH of VRLA cells in workshop.
Procedure to be followed in Workshop during POH: The below given instructions are to be followed when the coach comes for periodic overhaul { POH } to the workshop.
1. Remove all the cell terminal bolts, Flat washers, spring washers, inter cell cables, connectors etc. {use insulated tools only}
2. Care should be taken to avoid any shorting of cell terminals while removing inter cell cable connectors.
3. Remove the stacking bolts used for fixing battery modules to battery box/ cradle and between the trays.
4. Remove the modules with batteries from battery box/ cradle by using suitable tool.
5. Clean all the cell terminal posts and inter cell connectors/ cable lugs with a brass wire brush to remove any sulphated layer.
6. Refix the inter cell connectors/ cables and tighten the bolts along with flat and spring washers to specified torque. Replace old spring washers 100%. Quality of new spring washers should be checked as per IS 3063 especially permanent set test.
7. Discharge the battery bank at the rate of 0.1C and by pass each cell whenever it reaches end cell voltage of 1.75V.
8. Charge the cells at 7% constant current {77 Amps for 1100 Ah and 8.4 Amps for 120 Ah} for 15 hours.
9. Again give rest to the cells for 6-8 hours.
10. Discharge the cells at 12 Amperes for 120 Ah and 110 Amperes for 1100 Ah gradually by passing each cell whenever each cell reach 1.75 V. Duration of discharge shall be recorded. If the discharge duration of the cells is found to be more than 8 hrs these can be put back in service after charging.
11. If the cells do not give more than 8 hrs of discharge duration before reaching end cell voltage of 1.75 V, repeat this charging and discharging cycle once more. Cells should not be discharged below 1.75V .
12. Even then, if the cells do not give more than 8 hrs then the cells shall not be put in service.
13. Clean and repaint the modules/ cell trays. These may be numbered with the help of stenciling to identify the modules consisting of a battery set for a coach { say Module No / Set No. e.g. 08 /01 means 8th module of Set No. 1} . The other details like cell number, date of manufacture as indicated on the cell lid and date of fitment shall also be recorded to monitor age-wise performance of the cells.
Note: All the new VRLA cells shall be given a boost charging if the cells have been lying in the Depot / workshop for more than 6 month period from the date of manufacture.
QUESTION BANK FOR TRAIN LIGHTING COACHES
1. On what factors the output voltage of TL/AC alternator depends on?
Ans. The output voltage of TL/AC alternator depends on, speed of the rotor and level of field excitation.
2. Write about the working principle of TL/AC alternator?
Ans. The core of the stator which is completely embraced by the field coils will retain a residual magnetism if excited by a battery once. The flux produced by the filed coils find its path through the rotor. When the rotor is rotated the passage of rotor teeth and slots, alternatively, under the field, offers a varying reluctance path for the flux produced by the field coils. The flux, which varies periodically, links with AC coils and induces an alternating voltage in AC coil. The frequency of the induced voltage depends on the speed of rotor, where as the magnitude depends on the speed of the rotor and the level of excitation. The field is controlled through regulator to attain desired output voltage by means of positive feedback again.
3. What are the reasons for loss of residual magnetism? How do you regain it? What is the permissible and maximum DC voltage is to be applied to regain the residual magnetism?
Ans. The reasons for los of residual magnetism are keeping the alternator in idle condition for long time and connecting field wires in wrong polarity. To regain the residual magnetism flash the field terminals for correct polarity of DC supply. The permissible DC voltage is to be applied to regain the residual magnetism is 6 to 12V DC. Maximum voltage is 24V DC.
4. Explain the capacities of alternators used in TL/AC coaches?
Ans: The capacities of Alternators used in TL/AC coaches are
1. Train Lighting 110V system = 4.5 KW 130 Volts
2. Air Conditioning 110V BG coaches under slung = 18 KW 135 Volts
3. Air Conditioning 110V BG RMPU coaches = 22.5 KW 135 Volts = 25 KW 135 Volts
5. What is the purpose of belt-tensioning device? What are the parts it consists of?
Ans. The purpose of belt tensioning device is to keep V belts in tight condition. Its parts are
1. Tension rod
2. Tension spring
3. Belt tension indicator with spring seat
4. Fork eye
5. Fork eye side spring seat
6. Belt tightening nut 7. Free end pipe and nut
61. Explain working principle of KEL ALTERNATOR/REGULATORS 110 V, 4.5 K.W with the help of circuit diagram?
Ans . For easy understanding of KEL 3 & 4.5KW 30 volts alternator/rectifier regulator circuit diagram, was divided into four sub circuits. They are
1. Power supply circuit
2. Field circuit
3. Voltage control circuit
4. Current control circuit
1. Power supply circuit: This circuit consists of 3 phase alternator (ALT) & 3 phase bridge rectifier.(PR). Three phase AC supply (13,14,15 terminals) produced by alternator is fed to 3 phase bridge rectifier consists of 6 silicon power diodes. The bridge is protected against voltage surges by 6 numbers of 0.25 mfd capacitors (C1 to C6), One 10 mfd capacitor (C7) and one 10000pf capacitor (C8) are provided across the bridge for filtering DC output and protection against high frequency surges respectively. Shunt (26 amd 28) is provided in series to DC output voltage positive (+L) terminal,for sensing output current. DC output voltage terminals are(+L,-C) Function When the field coils are excited and rotor is rotated the variation in reluctance offered by the rotor teeth arrangement causes the flux produced by the field coil to pulsate. This pulsation of flux linked with Ac coils and induces e.m.f. in the AC windings. The induced e.m.f. in the 3 phase winding is rectified by the 3 phase bridge rectifier. The bridge rectifier also serves the purpose of maintaining the constant polarity in both the directions of the train and prevents current flowing from battery to alternator, when the coach is stable condition.
2. Field circuit: Field circuit consists of Excitation transformer (ET) Magnetic amplifier(MA),. Field rectifier (D2,D3) and Free wheeling diode(D4). And ET is an auto step up centre tapped transformer. It has three functions. 1. It is auto transformer having one winding 2. It steps up the voltage for good regulation of output voltage and current.
3. Its secondary winding is centre tapped used for full wave rectification with two diodes and accommodates load windings of MA. Magnetic Amplifier is used to control the field voltage and field current, there by controlling the output voltage and output current. It has six windings. Two are load windings connected in series to the field circuit. One winding is used for voltage control and one more winding is used for current control and other winding used as gain winding to boost output voltage when train is in slow speeds one more winding is spare. Free wheeling diode is provided to eliminate the surge voltage produced in the field coil. Cathode of free wheeling diode connected to field positive and anode to field negative. Two phase AC supply of Alternator given to ET primary (14 & 15 terminals) through field fuse F2. The centre tap secondary terminals (19) is connected to field negative (-EX) of alternator. The end terminals of ET secondary ( 18 &161) are connected to full wave rectifier (D2 &D3) through MA load windings (18,162 and 161,17). The rectified DC fed to field positive (+EX) of alternator through gain winding. (40 and 20). Free wheeling diode is connected across field terminals (19and20) in reverse direction. Function: The purpose of field circuit is to feed rectified DC supply for field for excitation. Two phase supply of alternator is stepped up by ET and rectified by full wave rectifier. This rectified DC is fed to field winding through gain winding. Free wheeling diode is provided to dissipate energy produced in the field, in other way to eliminate surge voltages produced in the field coil. 3. Voltage control circuit: This circuit consists of auxiliary rectifier(RT) (D5,D6,D7), voltage detector (DT) and voltage control winding of magnetic amplifier(10,11). The voltage detector consists of resistance network (R1,R2,R3,R4) and zener diode D8, 1k potentiometer (RH) is connected across the resistance R4 to vary the output voltage settings. Voltage detector serves the purpose of providing DC signal to the control winding of MA. Function: When the output voltage exceeds the present value, the drop across R1 is sufficient to conduct Zener diode and allows a DC signal to the voltage control winding of MA. The DC flux produced in control winding will oppose the AC flux of load winding and increases impedance of the field circuit. This increase of impedance, results in decrease of field voltage and field current there by decreasing output voltage. This process is continuous to maintain the output voltage constant. The voltage setting can be varied by varying the 1k potentio meter.
4. Current control circuit: This circuit consist of shunt resistance (SHR 26,28 terminals) shunt diode(D1) and current control winding of M.A(26and27). For sensing output current, SHR is provided in the DC output voltage of alternator. Shunt leads are connected to MA current control winding through shunt diode.
Function: When preset value of current is supplied by the alternator exceeds, the voltage drop across the shunt is sufficient to conduct shunt diode. When shunt diode conducts, it sends a DC signal to current control windings of MA. This DC signal induces DC flux in the windings. This Dc flux opposes the AC flux of load windings and increases the impedance of the field circuit. Increase of impedance in field circuit reduces the field voltage and field current there by decreasing the output voltage and output current. This process repeats when the output current exceeds and maintain the alternator current within preset limits. The current setting can be varied by varying the shunt resistance.
62. What are the precautions to be taken while loading and unloading of alternator?
Ans. i) While unloading and loading alternator, see that the terminal box and pulley should not be broken.
ii) The alternator to be loaded in correct way that bushes to be provided in proper place.
iii) While loading and unloading proper precautions to be taken not to fall on ground otherwise men/materials will be injured/damaged.
iv) See that the anti rotating clamp provided on trolley coincides with alternator suspension pin.
v) Replace the worn out alternator and alternator suspension bracket bushes.
vi) See that the alternator should not have play with proper washers in improper place to align the axle pulley.
vii) Safety chains and cotter pins to be provided without fail.
63. What are the Rating of various fuses in TL coach wiring system?
Ans. Main Battery Fuse is 40 A. L1,L2, Fan and EFT circuit fuses are 16 Amps HRC Main Negative fuse is of 35 amps HRC And Branch fuses are 35 SWG
64. What are the main components of Lead Acid cell?
Ans. Main components of Lead Acid cells are:
a) Positive Plates, which are tubular n shape, made of PBO2
b) Negative Plates, usually consists of lead grid into which active material of Sponge lead is pressed. c) Separators, which are made by Synthetic, used between Positive and negative plates.
d) Container is made of hard rubber or PPCP with high insulating strength to resist acids which are used as Electrolyte.
e) Cell cover which covers container having vent plugs and level indicator.
65. What is the Specific Gravity of fully charged lead acid cells?
Ans. The specific gravity of fully charged cell is in between 1.210- 1.220
66. What is meant by PPCP container?
Ans. Some cell container are made of PPCP which is called Poly Propylene Co-Polymer.
67. What is the SWG of DFB fuse?
Ans. The size of fuse wire 35 SWG is provided in Distribution Fuse board for each fan or light.
68. What is the wattage of 400 mm 110 V DC fan?
Ans. The Wattage of 400 mm DC fan in TL Coach is 35 Watts.
69. What is the specific gravity of sulphuric acid?
Ans. The specific gravity of sulphuric acid which is used to make electrolyte is 1.835.
70. What is the working voltage of 20 W/18W TL inverter?
Ans. The working voltage of 20W/TL inverter is 110 volts D.C.
71. What procedure is adopted to detect Earth leakage in a TL coach?
Ans. Double test lamp method.
72. Enumerate the cable sizes used in TL coaches?
Ans. Branch wiring : 4sq.mm Aluminium. LI,LII, and F+ve: 16 sq.mm Aluminium SPMI&II: 16sq.mm Aluminium Under frame wiring: Alternator to regulator Field winding -6sq.mm copper Main windings-16 sq.mm copper Regulator to under frame junction box: 35 sq.mm Al. UFJB to Battery box: 35 sq.mm Al
73. What is the maximum permissible voltage drop in TL coach?
Ans. The maximum permissible voltage drop allowed between the battery and any of the farthest light/fan point shall not exceed 3 volts at battery voltage of 108 +0/-2 volts.
74. What is the insulation tape used for insulation of cables in TL &AC coaches?
Ans. Flame retardant low-tension tape. 75. What method of charging is used for Lead acid cells and VRLA cells during POH? Ans. Constant current method of charging is adopted.
76. Give important measures adopted by railways for prevention of fires in TL coaches?
Ans. a) Cable sizes have been standardized.
b) Provision of re-wirable fuse on both positive and negative side in the distribution fuse board
c) Use of self extinguishing PVC cables.
d) Provision of rubber grommets at points where the cable enters through metal members in the coach.
f) Proper crimping at the cable terminals.
g) Air clearance of 10 mm between live part and earth and between parts of opposite polarity.
h) Replacing of cables with any joints, noticed during POH.
i) Re-wiring of the coach planned on the basis of cable life of 20 years.
j) Use of Flame retardant Insulation tape.
k) Checking of coach wiring by double test lamp method.
77. What precautions will you take during re-wiring of a coach?
Ans. a) Use of PVC cables of suitable current.
b) In under frame and end walls of coach the wiring has to be drawn through Rigid steel conduits
c) Use of proper size of fuses.
d) The phase and field wires from the Alternator to terminal box shall be run in one flexible PVC conduit and from terminal box to rectifier – cum-regulator & from rectifier-cumregulator to under frame terminal board in one rigid steel conduit.
e) Proper method of crimping by using proper die and use of corrosion inhibiting compound during crimping of Aluminium cables.
f) Segregation of positive and negative cables. g) Cables in the roof (super structure) to be carried in non-metallic rigid conduits with proper cleating arrangement.
h) Use of FRLT insulation tape.
i) After re-wiring the test the insulation resistance with 500v dc megger. The minimum insulation resistance should be 2 Mega ohms.
24. Procedure to maintain correct tension of new ‘V’ belts on bogie transform mounted alternator of AC Coaches and non AC coaches.
Ans. 1. Provide alternator on the bogie.
2. Provide axle pulley on the wheel.
3.Provide ‘V’ belt of matching set between grade 48 & 52 on wheel axle, on which, the axle pulley is provided.
4. After lowering and completion of buffer head adjustment of bogie, provide ‘V’ belts over alternator towards the axle pulley.
5. After completion of provision of V belt, remove the split pin check nut and fixing nut of free end side tension rod spring tightening collar nut.
6. Free the check nut and fixing nut of U clamp side of tension rod.
7. Now insert the tension rod assembly between the bogie supporting bracket and eye (leg) of the alternator.
8. Provide bolt for ‘U’ clamp of tension rod and eye of the alternator.
9. Then slowly tighten the fixing nut (U clamp side) unit tension indicator match with the spring collar. This will give the correct tension of the V belt.
10. Then provide fixing nut, check nut and split pin leaving a gap of 75 mm for AC coaches and 55 mm non AC coaches at free end side of tensioning for mechanism.
11. Then observe the tension of belt.
25. What are the advantages and disadvantages of 110 Volts DC Train lighting System?
Ans. Advantages:
1. The demand for better passenger amenities like improved illumination, provision of tube lights with inverters, provision of water coolers/refrigerators can be achieved in this system.
2. For the same loads, the current handled is only 21.8% therefore cables and connectors are smaller in size.
3. The ratio of short circuit current and the normal full load will be high. Therefore faults discrimination better in 110 V systems.
4. Florescent lights can be used with the aid of electronic invertors (without choke and bulb).
5. Higher coach loads can be handled with the higher generation capacity to meet the additional amenities like. Provision of fluorescent lamps in sleeper coach. Provision of more fans in sleeper and GS coaches. Provision of water coolers in coaches etc. Due to current flowing in the circuits is low the voltage drop reduced to minimum the illumination in the coaches is improved.
6. In the 110V DC system, the size and weight of the cells reduced considerably easy to handle.
7. Bogie transform mounted alternators with V belts are provided to avoid theft of belts and alternator parts.
Disadvantages:
1. In the 120 volts system single battery is provided load on the battery is more. The life of the battery is reduced considerably.
2. Due to introduction of transform mounting system the complete coach has to be lifted for replacement of V belts.
3. Due to provision smaller size batteries, the quantity of electrolyte is limited. If the level of electrolyte is not maintained by adding distilled water, the batteries may damage.
4. Due to high voltage system, requires high value of insulation resistance for safety etc.
26. What are the major train lighting equipment available in Self Generating coaches and explain about them briefly?
Ans. The major train lighting equipment in coach are
1. Alternator
2. Rectifier cum Regulator Unit
3. Battery
4. Axle Pulley
5. Rotary/ Roof Junction Box
6. Under frame Junction Box
7. Fans
8. Lights
9. EFT
10. BCT
27. Draw the schematic diagram of 110 Volts DC TL system including capacities of equipment and protective devices?
Ans. Schematic diagram of 110 v DC TL system Major Equipment: Alternator 4.5 kw R R U 110 V DC 32A 120 Ah BCT R/S 40A 16 A L-1 L-2 F-1 SPM RJB (+)FDB 6A 6A - ve fuse 35 A (-) FDB - ve + ve
Alternator - 4.5 kw, 110V, 3 phase, brush less type, totally enclosed, reversible shunt wound.
Regulator Board (RRU/ERRU) - 4.5 kw.
- Battery - 120 Ah, 110 V DC, lead acid / VRLA type
- Light: - 25 w /20w, 110v DC.
- Fans:- 40 w
- V-belts, axle pulley & alternator pulley Protective device:
- OVP
- HRC fuse (32 A/40 A, 16A, 6A)
- Rotary switch (40 A)
28. Draw the neat Coach Wiring Diagram of 110V DC TL system including capacities of equipment and protection devices? Diagram Of 110 Volts DCTL System Including Capacities Of Equipment And Protection Devices
MAJOR EQUIPMENTS IN TL COACH:
- Alternator – 4.5 kw, 110V, 3phase, brush less type, totally enclosed, reversible shunt wound
- Regulator Board-4.5 kw
- Battery-120 Ah, 110V DC, lead acid / VRLA type
- Light -15 w / 20w.110V DC Fans-40w
- V-belts, axle pulley, alternator pulley
PROTECTIVE DEVICE:
- OVR / OVP HRC fuse ( 40 A , 16 A, 6A)
- Rotary switch (40 A)
29. What are the sizes / capacity of fuses provided at various locations of 110 Volts Train Lighting coach? Ans. Sl. No. Circuit fuse Location Fuse size Current rating 1. 2. 3. 4. 5. 6. 7. Positive/negative SPM1 & SPM2 Main negative L1, L2, and F +ve Battery fuse Field fuse AC fuse Branch fuses Junction box J/Box J/Box Battery box Regulator box Regulator box DFB 35 SWG RW 16A HRC 35A HRC 16A HRC 40A HRC 6A HRC 20 35A HRC 6A --- --- --- --- 6A --- ELECTRONIC RECTIFIER CUM REGULATOR UNIT (ERRU)
30. What are the advantages and disadvantages of ERRU? Advantages of ERRU:
1. Control circuit is Modular type design.
2. Auto identification of alternator ratings and indications.
3. Auto setting of parameter of voltage, load current, Battery current, over voltage, over current and current limiting for all the regulator of 4.5 kw, 18kw and 25kw.
4. UVC is interchangeable with all types of electronic regulators from 4.5 kw to 2.5 kw.
5. Close regulation of voltage +/-2 V over the entire range of load and speed to have uniform charging of batteries.
6. Less voltage and current ripple on Battery Charging current.
7. Controlled battery charging current to have longer life of batteries.
8. Moduled Hall sensors for current sensing and setting current limit.
9. Static over voltage protection and latching without battery.
10.Isolated power packs directly mounted on the heat sinks to have better heat dissipation. 11.Moulded PCBs to avoid dust and vibration problems.
12.Separate interface unit for monitoring the parameters like DC Voltage, DC current, Battery charging and discharging currents, Amps Hours etc.
13.This interface facilities to store AH.IN and AH.OUT. generation and non-generation time, total distance travelled by coach and faults occurred in the regulators.
14.This interface also has Emergency unit. In case of failure of one control unit, the other control unit will take care of both regulators.
Disadvantages of ERRU:
1. Sophisicated electronic equipment.
2. Qualified staff are required for maintenance.
3. Costlier than MA type regulator.
4. If PCB failed entire PCB to be changed.
5. For repairing ERRU on test bench, Alternator supply must be required.
6. Alternator setting can not be adjusted manually on test bench.
7. Costlier spare parts are to be stocked.
31. What are the important parts of ERRU? Important parts of ERRU:
1. Iso pack power diodes
2. Universal voltage controller
3. IGBT controlled field circuit
4. Hall sensor
5. Static over voltage protection
6. Interface unit
7. LED/alpha numerical display
Universal Voltage Controller (UVC): This is an electronic controller unit having microprocessor/micro-controller/PWM controller which is common for all ratings i.e.25KW/18 KW & 4.5 KW of alternators and respective ERRU having different power circuits. UVC should be able to identify the rating of the alternator and automatically adjusting the setting parameter as per this specification according to the rating of the alternator and battery. The UVC controls the field current to maintain the set output voltage of the alternator. The field circuit is provided with IGBT. The gate of the IGBT is controlled by micro-controller, which is programmed with all data as per the requirements of the specification. UVC gets the power from power supply modular. Universal Voltage Controller shall be equipped with micro processor/ micro controller/ PWM controller to meet the various requirements laid down. Wherever possible, adequate design redundancy to take care of controller failure from total system failure/hanging. The design of every UVC shall have provision to ensure proper load sharing between two alternators provided on the same AC coach and the difference of load sharing shall not be more than 10A enabling to achieve high reliability of alternators avoiding continuous overloading of one alternator. There shall also be a provision of communication between two ERRU running in parallel. The UVC of ERRU of different rating i.e. 4.5 KW and 215 KW shall have universal application with a common design to achieve inter changeability among the same make. The manufacturer shall have to declare their design and its capacity. The UVC shall be suitable to work with 25 KW & 4.5 KW capacity alternators in the existing field conditions. UVC shall preferably have following features for improving reliability.
UVC shall preferably equipped with minimum of 16 bit industrial micro process/ micro controller with built in USB and PWM control ports.
No through hold type of micro processor/micro controller should be used for high reliability.
External programmed memory should not be used with micro processor/ micro controller for highest reliability of memory fetching.
The PCB design of UVC shall be done only on single card to eliminate the inter connection between PCB and easy service on card replacement basis.
Only sealed membrane key pads should be used along with UVC for highest reliability.
The discrete power supply for powering the UVC micro processor / micro controller must be electrically isolated from coach battery DC power. Following indication shall be available on UVC / display unit in case of 4.5 KW whereas for 25 KW ERRU on UVC and CIP.
Capacity of alternator
Healthiness of UVC IGBT’s used in field circuit:
IGBT : Insulated Gate Bi-polar Transistor – a semi conductor devices used as switching ‘on’ and ‘off’ to control DC input signal to the field for regulating DC output in ERRU. IGBTs are semi conductors that combine a high voltage and high current bipolar junction transistor (BJT) with low power and fast switching metal oxide semiconductor field effect transistor (MOSFET). Consequently IGBTs provide faster speeds, better drive and output characteristics than power BJTs and offer high current densities than equivalent high powered MOSFETs.
Over Voltage Protection in ERRU: OVP: Over Voltage due to component failure/ open circuit in regulator, over voltage protection circuit should be provided with no nuisance tripping under no-load or load condition. During sudden throwing of load (without battery connected) the over voltage relay may, over voltage protection circuit should be provided with no nuisance tripping under no-load or load condition. During sudden throwing of load (without battery connected) the over voltage relay may trip but must reset by itself automatically. Latching of the relay may be achieved under fault condition with battery supply available at the DC output. Certain time delay may be provided for relay operation so that the relay does not trip when load is thrown off suddenly with battery connected. However the time delay provided should be less than 2 sec. in order to protect the system under genuine fault conditions. The tripping voltage of the relay may be set between 138+- 1 volts. Software OVP shall be at 138+- 1 volts where as separate OVP shall be set at 141 +- 1.
LED / alpha numerical display used in ERRU: The UVC shall also be provided with an indication board with LED/ALPH-numerical display to indicate its various status as given below.
1. Capacity of alternator 2. Healthiness of UVC (failure status)
3. Over voltage protection
4. Functional status under emergency
5. Alternator failure
6. Fuse failures phase/ control
7. Overload/ Short circuit
8. Battery charging/ discharging Ah over a duration
42 OBJECTIVE TYPE QUESTIONS MULTIPLE CHOICE ON AIR CONDITIONING SYSTEM
1. The cooling coil in AC system is called
a) Evaporator
b) Condenser
c) Both (a) and (b) d) None
2. The accepted humidity for human comfort is about
a) 40-60% b) 80-100% c) 20-40% d) None
3. The accepted temperature for human comfort during summer is
a) 72°F to 78°F
b) 62°F to 68°F
c) 82°F to 88°F
d) 52°F to 58°
4. The accepted temperature for human comfort during winter is
a) 72°F to 78°F
b) 62° c) 82°F to 88°F
d) 52°F t
5. The purpose of condenser used in vapour compressor system is a) It controls the rate flow of high pressure refrigerant liquid b) It allows refrigerant liquid to evaporator at low pressure c) Both (a) and (b) d) None
6. The purpose of de-hydrator and filter used in vapour compressor system is a) It removes moisture available in refrigerant system b) It prevents particles and scales in refrigerant system c) Both (a) and (b) d) None
7. The danger for the human body, if the temperature falls below
a) 98°F
b)98.6°F
c) 105.6°F
d)None
8.The temperature of air recorded by a thermo meter, when it is not affected by the moisture present in it, is called
a)Wet bulb temperature
b)Dry bulb temperature
c)Dew point temperature
d)None of those
9. Evaporator changes the low pressure liquid refrigerant into
a) High pressure liquid refrigerant
b)Low pressure vapour refrigerant
c) Very high pressure liquid d) None
10. During a refrigerant cycle, heat is rejected by the refrigerant at
a) Compressor
b)Condenser
c)Evaporator
d)Expansion valve
11.Psychometric chart shows relationship between
a) Dry bulb temperature
b) wet bulb temperature
c) Dew point temperature
d)Humidity
e) Total heat (enthalpy)
f) All of the above
12. The purpose of air condition is
a) Temperature control
b) Humidity control
c) Air movement and circulation
d) Air filtering, cleaning and purification
e) All of the above
13. The unit for the capacity of air conditioning is in
a)Ton of refrigeration
b) Kilograms
c) Founds d) None
14. One ton of refrigerant is equal to
a) 3000 Kcal/hour
b) 12000 BTU/hour
c) Both (a) and (b) d) None
15. The cooling in the coach is not sufficient, the reasons may by
a) Compressor not getting loaded/poor efficiency
b) Too little gas or air may have accumulated in the system
c) Condenser, fresh/return filters, evaporator dirty/choked
d) Setting of expansion valve disturbed e) All of the above.
16. Excessive cooling in the coach is due to
a) System working continuously due to fault in the control system b) System kept in manual cooling
c) Compressor defective
d) both (a) and (b)
17. The function of capillary tube is same as
a) Condenser
b) Evaporator
c) Compressor
d) Expansion valve
18. RMPU means
a) Roof mounted package unit
b) Rail mounted package unit
c) Rack mounted package unit
d) None
19. Refrigerant is used in RMPU is
a) R.22
b) R.12
c) R 134a
d) None
20. Chemical name of R.22 is
a) Monochloro difluoromethane CHCIF2
b) Dichloro diflouro methane CCl2F
c) Dichloro monoflouro methane CHCl2F
d) None
21. Quantity of Refrigerant to be charged for one AC circuit of RMPU is about
a) About 3kgs
b) About 20kgs
c) About 30kgs
d) None
22. Power supply is fed to compressors and condenser and evaporator units of RMPU coach is
a) 1 phase 230 v
b) 3 phase 415 V
c) 3 phase 110 V
d) None
23. Capacity control of RMPU is
a) 50% to 100%
b) 25% to 100%
c) 75% to 100%
d) None
24. Capacity in tone of refrigeration of one RMPU has
a) 14tons
b) 5.2 tons
c) 7tons
d) None
25. The power required for one RMPU is about
a) 13 KW
b) 5.75KW
c) 23 KW
d) None
26. The current taken by the one RMPU unit is
a) 40A
b) 22 A
c) 10 A
d) None
27. The capacity of compressor motor used in RMPU AC coach is
a) 5.25 KW
b) 5 .3 KW
c) 4.3 KW
d) None
28. The capacity of condenser motor used in RMPU AC coach is
a) 1 HP
b) 1.5 HP
c) 2.5 HP
d) None
29. The capacity of evaporator fan motor of RMPU AC coaches
a) 1.5 HP
b) 0.5 Hp
c) 2.5 HP
d) None
30. Heater load of one RMPU is about
a) 6 KW
b) 3KW
c) 12KW
d) None
31. Current taken by one compressor motor of RMPU AC coach is
a) 8.25+/-25%
b) 2.6+/-10%
c) 2.2+/-10%
d) None
32. Speed of the condenser motor of RMPU coach is
a) 910 RPM
b) 720 RPM
c) 2880 RPM
d) None
33. Speed of the evaporator fan motor of RMPU coach is
a) 1415 RPM
b) 720 RPM
c) 2880 RPM
d) None
34. The capacity of inverters used in RMPU coach is
a) 18KVA
b) 25KVA
c) 12KVA
d) None
35. Motors used in RMPU coaches are
a) Induction motors
b) Synchronous motors
c) Slip ring induction motors
d) None 36.HP cut out of RMPU
coach shall be set at
a) 135+/-15% PSI
b) 415 +/-15%PSI
c) 35 +/- 15% PSI
d) None
37. LP cut out of RMPU coach shall be set at
a) 135+/-15% PSI
b) 415 +/-15%PSI
c) 35 +/- 15% PSI
d) None
38. The OHP thermostat shall be set to operate at
a) 200°C
b) 150°C
c) 100°C
d) None
39. The cooling temperature settings of electronic thermostat are recommended by RDSO is
a) 23°C,25°C
b) 22°C,25°C
c) 24°C,26°C
d) None
40. The heating temperature settings of electronic thermostat are recommended by RDSO is
a) 17°C,19°C
b) 19°C,21°C
c) 21°C, 23°C
d) None
41. Number of vane relays required for one RMPU are
a) 2
b) 1
c) 4
d) None
42. Capacity of WRA used in RMPU coaches
a) 0.5 HP/0.37 KW at 415 V, 50 HZ,PF 0.5
b) 1.0 HP/0.746 KW at 415 V, 50 HZ, PF 0.5
c) 1.5 HP/1.1 KW at 415 V, 50 HZ PF 0.5
d) None
43. The capacity of control transformer provided in RMPU AC coach is
a) 400 VA
b) 1000 VA
c) 2500 VA
d) None
44. The duration of TDRI delay setting is
a) 2 min
b) 2.5 min
c) 3.5 min
d) None
45. The duration of TDRII delay setting is
a) 2 min
b) 2.5 min
c) 3.5 min
d) None
46. Over load setting range of blower motor of RMPU
a) 0.8 to 1.4 A
b) 1.5 to 2.5 A
c) 7 to 10.5 A
d) None
47. Over load setting range of condenser motor 1 & 2 of RMPU
a) 0.8 to 1.4 A
b) 1.5 to 2.5 A
c) 7 to 10.5 A
d) None
48. Over load setting range of compressor motor 1 & 2 of RMPU
a) 0.8 to 1.4 A
b) 1.5 to 2.5 A
c) 7 to 10.5 A
d) None
49. The purpose of auxiliary contactor AC1 provided in control panel of AC coach is
a) To switch on control supply to condenser motors I & II
b) To switch on control supply for compressor motors I & II
c) To switch on control supply to heaters I & II
d) To switch on control supply to entire control circuit except blower circuit
50. The purpose of vane relays 1 & 2 provided in the RMPU AC system is to
a) Not to switch ON condenser motors in case of blower failure
b) Not to switch ON compressor motors in case of blower failure
c) Not to switch ON heaters in case of blower failure
d) Not to switch ON entire AC system in case of blower failure
51. The cut in pressure of the reciprocating compressor type WRA used in RMPU coach is
a) 0.3kg/sq cm
b) 0.75 kg/sq cm
c) 1.7 kg/sq cm
d) None
52. The cut out pressure of the reciprocating compressor type WRA used in RMPU coach is
a) 0.3kg/sq cm
b) 0.75 kg/sq cm
c) 1.7 kg/sq cm
d) None
53. In RMPU Ac coaches, the type of expansion valve used is
a) Capillary tube
b) Thermostatic expansion valve
c) Constant pressure expansion valve
d) None
54. In under slung AC coaches, the type of expansion valve used is
a) Capillary tube
b) Thermostatic expansion valve
c) Constant pressure expansion valve
d) None
55. The recommended refrigerant in place of R 12 is
a) R22
b) R134a
c) R100
d) None
56. The type of cables to be provided in new air conditioned coaches
a) Elastomeric copper cables
b) PVC copper cables
c) E-Beam irradiated thin walled elastomeric cables
d) None
57. To avoid fires in AC coaches the minimum clearance between live part and coach body should be a) 4mm
b) 2mm
c) 3mm
d) None
58. To avoid fires in the AC coaches, tape should only be used is
a) The insulating fire retardant low tension (FRLT)
b) PVC
c) Cotton tape
d) All the above
59. Capacity of battery used in RMPU AC coach other than first class is
a) 800AH
b) 1100AH
c) 540AH
d) None
60. Capacity of battery charger used in RMPU AC coach is
a) 200/250 A
b) 40A
c) 70A
d) None
61. Number of lead acid cells available in battery of SG RMPU AC coach
a) 56
b) 54
c) 112
d) None
62. The capacity of HRC fuses to be provided for 1100AH battery of SG RMPU AC coach is
a) 400A
b) 250A
c) 100A
d) None
63. The capacity of plant selector rotary switch RSW2 provided in power panel of RMPU AC coach is
a) 300A
b) 400A
c) 63A
d) None
64. The capacity of HRC fuses both positive and negative to be provided for plant selector circuit in power panel of RMPU AC coach is
a) 400 A
b) 250 A
c) 63 A
d) None
65. The capacity of power selector4 rotary switch RSW1 provided in power panel of RMPU AC coach is
a) 500 A
b) 160 A
c) 16 A
d) None
66. Refrigerant used in under slung AC unit is
a) R22
b) R134a
c) R407C
d) None
67. Compressor system design of under slung AC unit is
a) Open
b) Hermitically sealed
c) Semi sealed
d) None
68. Capacity control of AC under slung unit is about
a) 25% to 100%
b) 50% to 100%
c) 75% to 100%
d) None
69. The system of voltage of under slung AC coaches are
a) 110/135 DC
b) 415V AC
c) 750V AC
d) None
70. The capacity of battery is provided in AC under slung coaches single set of
a) 525 AH 56 cells
b) 800 AH 56 cells
c) 1100 AH 56 cells
d) None
71. The capacity of first class under slung AC system is
a) 5.2 TR
b) 6.7 TR
c) 7TR
d) None
72. Capacity of condenser motor used in first class under slung air condition system
a) 1.0 KW
b) 0.75 KW
c) 2 KW
d) None
73. The capacity of evaporator fan motor used in first class under slung AC coach
a) 1 KW
b) 0.65 KW
c) 1.5 KW
d) None
74. The speed of the condenser fan motor used in AC first class under slung AC coach
a) 1500 RPM
b) 2800 RPM
c) 750 RPM
d) None
75. The speed of the evaporator fan motor used in AC under slung system
a) 1500 RPM
b) 3000 RPM
c) 700 RPM
d) None
76. The total capacity of AC system used in AC two tier and AC composite coach
a) 10.4 tons
b) 13.4 tons
c) 14 tones
d) None
77. The capacity of alternator used in under slung AC chair car, AC sleeper coach, AC composite coach are
a) 18 KW 135V
b) 12 KW 135 V
c) 25 KW 135V
d) 22.5 KW 135V
78. When under slung AC coach is working in normal condition the section pressure gauge reading should be
a) 37-40 PSI
b) 150 to 170 PSI
c) 135 to 150 PSI
d) None
79. When under slung AC coach is working in normal condition the delivery pressure gauge reading should be
a) 37-40 PSI
b) 150 to 170 PSI
c) 50 to 70 PSI
d) None
80. The oil pressure of the compressor is
a) 70 to 90 PSI
b) 150 PSI
c) 200 PSI
d) None
81. Recommended setting of low pressure cut out of under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI
d) None
82. Recommended setting of low pressure cut out of under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI
d) None
83. Recommended setting of high pressure cut out of under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI
d) None
84. Recommended setting of oil pressure cut out for ACCEL and CARRIER in under slung AC coach is
a) 10 PSI
b) 250 PSI
c) 25 PSI above section pressure
d) None
85. The purpose of low voltage relay (LVR) used in control panel of under slung AC coach is
a) Stop the compressor motor/condenser motor, heaters if the battery voltage less than 100V
b) It cuts of the supply to control circuit
c) It will reset if the battery voltage rises to 102 V
d) All of the above
86. In under slung AC coach, the rating of fuseF2 + provided for protection of heater
a) 125A
b) 63A
c) 10A
d) 2A
87. Recommended grades of oil for compressor are
a) Frezol 3
b) Sheftal 68
c) Servo FreeZ-71
d) Servo FreeZ-66
e) All of the above
88. Chemical name of refrigerant R 134a
a) Dichloro difluoro methane
b) Chloro difluoro methane
c) Tetra fluoro ethane
d) None
89. Size of carbon brushes used in compressor motor of under slung AC in
a) 44.3 x 25.75 x 939 mm x 2
b) 44.5 x 25.4 x 9.52 mm x 2
c) 40 x 32 x 16 mm
d) All the above
90. Size of carbon brushes used in condenser motor of under slung AC in
a) 32 x 20 x 10 mm
b) 32 x 20 x 8 mm
c) 32 x 8 x 10 mm
d) All the above
91. Size of carbon brushes used in condenser motor of under slung AC in
a) 32 x 20 x 8 mm
b) 32 x 22 x 8 mm
c) Both a & b
d) None
92. An electrolyte use in train lighting cell is the mixture of
a) Sulphuric acid and tap water
b) Sulphuric acid and mineral water
c) Sulphuric acid and demineralized/distilled water
d) None of the above
93. When cell is fully charged, the positive plate becomes
a) Lead peroxide
b) Spongy lead
c) Lead sulphate
d) None
94. When the lead acid cell is fully charged the negative plate becomes
a) Lead peroxide
b) Spongy lead
c) Lead sulphate
d) None
95. The capacity of cell is measured in
a) Ampere hour
b) Watt hour
c) Amperes
d) Watts
96. Internal resistance of lead acid cell is mainly due to
a) Size of plates
b) Distance between the plates
c) Nature of electrolyte
d) All the above
97. Trickle charging of storage battery help to
a) Compensate for internal losses
b) Maintains proper electrolyte
c) Increase its capacity
d) None
98. The capacity of Battery used in 110V T.L system
a) 120AH
b) 210Ah
c) 320Ah d) 90AH
99. SPGR of fully charged cell
a) 1.220
b) 1.180
c) 1.140
d) 1.100
100. SPGR of half charged cell
a) 1.210
b) 1.175
c) 1.100
d) 1.140
101. SPGR of fully discharged cell is
a) 1.210
b) 1.175
c) 1.200
d) 1.140
102.Total number of cells available in TL Battery of 110V system
a) 54
b) 56
c) 24
d) 18
103. Sulphation occurs due to
a) Cells kept under discharged condition
b) Cells kept under not fully charged condition
c) Cells over charged
d) All the above
104. The codal life of lead acid TL/AC cells is
a) 4
b) 3
c) 2
d) None
105. The capacity of batteries used for RMPU AC coaches is
a) 525 AH
b) 400 AH
c) 800 AH
d) 1100 AH
106. VRLA Batteries works on
a) Oxygen recombination principle
b) Hydrogen recombination principle
c) Hydrogen-oxygen recombination principle
d) None of the above
107. Normally the VRLA cells mounted in a position.
a) Horizontal
b) Vertical
c) Slanting
d) None
108. VRLA battery separators can be of
a) The gelled electrolyte type
b) The absorbed electrolyte type
c) A & b d) None of the above
109. Conductivity is the ability of a solution to conduct electrical current commonly expressed in
a) Amperes
b) Watt
c) Micro mhos/cm
d) None
110. Conductivity of DM water is measured by
a) Conductivity meter
b) Universal solution
c) pH meter
d) all of the above
111. Acceptable quality of treated water conductivity is in micro mhos/cm
a) <10
b) <30
c) 40
d) None
112. Acceptable quality of treated water PH value will be
a) 6.8 to 7.2
b) 7.5 to 8.5
c) 8.5 to 10
d) None
113. Inverters convert
a) AC into DC
b) DC into AC
c) Both a & b
d) None
114. In 25 KVA inverter the 3 phase AC supply is achieved by boosting DC voltage 100/140 volts into
a) 230V DC
b) 650V DC
c) 415V DC
d) None
115.Out put PWM voltage of inverter section of 25 KVA inverter of RMPU AC coach is
a) 650VDC
b) 220VDC
c) 24V DC
d) 3 phase 415 V AC
116.Alternator is a device that converts
a. Mechanical energy into electrical energy
b. Electrical energy into mechanical energy
c. Chemical energy into electrical energy
d. None of the above
117. Both field winding and 3 phase winding of AC coach alternator 120V are provided on _________
a. Stator
b. Rotor
c. Both a and b
d. None
118.TL/AC coach alternator 120V designed to have ______________
a. Residual magnetism
b. Permanent magnetism
c. Both a and b None of the above
119.Recommended Cut in speed of 4.5 KW TL alternator is by RDSO with MA RR unit ___________
a. 357 rpm
b. 600 rpm
c. 1100 rpm
d. 2500 rpm
120.Minimum speed for full output of 4.5 KW 120V TL alternator, recommended by RDSO is _______
a. 357 rpm
b. 600 rpm
c. 1500 rpm
d. 2500 rpm
121.Maximum speed of TL/AC coach alternator is
a. 400 rpm
b. 800 rpm
c. 1500 rpm
d. 2500 rpm
122.Field coils of 120V TL/AC coach alternator are connected in
a. Series
b. Parallel
c. Star
d. Delta
123.Three phase windings of 120V TL/AC coach alternator are connected in
a. Star
b. Delta
c. Series
d. Parallel
124.Size of V belts used for driving 110V, 4.5KW TL alternators
a. C122
b. C118
c. C124
d. None
125.Size of V belt used for driving 110V, 18, 22.5KW AC coach Alternators
a. C122
b. C118
c. C124
d. None
126.Number of V belts used for driving 110V, 4.5KW TL alternator is ___________
a. 4
b. 6
c. 12
d. None
127.Number of V belts used for driving 110V, 18, 22.5, 25KW AC alternator is ___________
a. 4
b. 6
c. 12
d. None
128.DC output voltage of Alternator /Regulator of 110V, TL/AC coach is
a. (110-140) DC
b. (70-90) DC
c. (90-120) DC
d. None
129.Rated DC output current of 4.5KW 110V, Alternator is ____________
a. 37.5A
b. 19A
c. 43A
d. None
130. Rated DC output current of 18KW 110V Alternator is ____________
a. 193A
b. 175A
c. 135A
d. None
131. Rated DC output current of 25KW 110V Alternator is ____________
a. 193A
b. 175A
c. 135A
d. None
132. Pitch circle diameter of Axle pulley of 110V TL system
a. 200mm
b. 140mm
c. 5726mm
d. None
133.Pitch circle diameter of Axle pulley of 110V AC coach system
a. 200mm
b. 584mm
c. 572.6mm
d. None
134.As per the latest SMI, the voltage setting of alternator 4.5KW 110V for passenger train with flooded batteries is ____________
a. 127V DC b. 124V DC
c. 122V DC d. None 135.As per the latest SMI, the voltage setting of ac alternator 18KW 110V with flooded batteries is
a. 129V DC
b. 124V DC
c. 122V DC
d. None
136.As per the latest SMI, the voltage setting of alternator 4.5KW 110V for passenger train with VRLA batteries is ____________
a. 123+/-0.5V DC
b. 124+/-0.5V DC
c. 121+/-0.5V DC
d. None
137.As per the latest SMI _____the voltage setting of alternator 4.5KW 110V for mail/express trains with VRLA batteries is ____________
a. 123+/-0.5V DC
b. 124+/-0.5V DC
c. 121+/-0.5V DC
d. None
138.As per the latest SMI the voltage setting of alternator 4.5KW 110V for super fast trains with VRLA batteries is ____________
a. 123+/-0.5V DC
b. 124+/-0.5V DC
c. 121+/-0.5V DC
d. None
139.As per the latest SMI the voltage setting of AC coach alternator 110V for passenger train with VRLA batteries is ____________
a. 128+/-0.5V DC
b. 127+/-0.5V DC
c. 126+/-0.5V DC
d. None
140.As per the latest SMI the voltage setting of AC coach alternator 110V for Mail/express train with VRLA batteries is ____________
a. 128+/-0.5V DC
b. 127+/-0.5V DC
c. 126+/-0.5V DC
d. None
141.As per the latest SMI the voltage setting of AC coach alternator 110V for super fast train with VRLA batteries is ____________
a. 128+/-0.5V DC
b. 127+/-0.5V DC
c. 126+/-0.5V DC
d. None
142.The purpose of TL Alternator used in Railways.
a. Charging the coach battery on train run
b. Working of lights and fans in the coach during train run
c. Sharing the load to other coaches in case of emergency
d. All the three above
143.The capacity of alternator used for BG coach 110V Train Lighting system.
a. 3KW
b. 4.5KW
c. 12KW
d. None
144.The capacity of alternator used for BG coach 110V roof mounted AC coach
a. 12KW
b. 18KW
c. 25KW
d. None
145.The capacity of alternator used for BG coach 110V under slung AC coach.
a. 25KW
b. 12KW
c. 18KW
d. None
146.The PCD (pitch circle diameter) of 25KW 110V alternator pulleys is
a. 584mm +/- 0.4mm
b. 200+/-0.3
c. 140 mm
d. 100 mm
e. None
147.The field resistance of 4.5KW 110V TL alternator has
a. 4.5 +/-0.5 ohms
b. 6.0+/-0.5 ohms
c. 10+/-0.5 ohms
d. None
148.The resistance between two phases of 4.5KW 110V TL alternator is
a. 0.4 +/-0.05 ohms
b. 0.8 +/-0.10 ohms
c. 4.5 +/-0.5 ohms
d. None
149.The purpose of providing anti rotating clamp near suspension arrangement of alternator is
a. Not to rotate suspension pin of alternator
b. Not to damage the nylon bushes of alternator/ suspension bracket
c. Not to damage the suspension bracket/boss of alternator
d. All of the above
150.The insulation material recommended for alternator windings of 3&4.5 KW 110V shall be __________ class.
a. A
b. B
c. F
d. None
151.The voltage setting of Alt/RR unit is to be set in far with current and RPM for 4.5KW is
a. Half rated capacity of the alt as load as 1500 RPM
b. ¼ rated capacity of the alt as load at 1000 RPM
c. Full rated capacity of alt as load at 2550 RPM
152.While measuring insulation resistance of 110V alternator/rectifier cum regulator the rating of megger is to be used is
a. 100V DC megger
b. 500V DC megger
c. Both a and b
d. None
153.The resistance between two phase of 25KW KEL alternator is about
a. 0.0530746 ohms
b. 0.034 to 0.038
c. 44.2 mille ohms
d. None
154.The field resistance of 25KW KEL alternator about
a. 9.7568 ohms
b. 8+/-0.5 ohms
c. 10.72 ohms
d. None
155.The gap between two halves of axle pulley to be maintained is
a. 3.0 +/-0.5 mm
b. 6mm +/- 0.5 mm
c. 4mm +/- 0.5 mm
d. None
156.Codal life of 4.5, 18, 22.75 & 25 KW alternator / RR unit
a. 12 years
b. 25 years
c. 15 years
d. None
157.Codal life of 120 AH VRLA Battery
a. 5 years
b. 4 years
c. 3 years
d. None
158.Codal life of 120 AH Flooded Battery
a. 5 years
b. 4 years
c. 3 years
d. None
159.Codal life of Battery charger
a. 12 years
b. 15 years
c. 25 years
d. None
160.Codal life of Coach wiring
a. 12 years
b. 15 years
c. 20 years
d. None
161.Codal life of Carriage fans
a. 10 years
b. 12 years
c. 15 years
d. None
162.The distance to be maintained while fixing axle pulley on wheel, from wheel hub to axle pulley outer wedge for 25 KW alternator is
a. 225 mm
b. 240 mm
c. 145 mm
d. None
163.The distance to be maintained while fixing axle pulley on wheel, from wheel hub to axle pulley outer wedge for 18 KW alternator is
a. 225 mm
b. 240 mm
c. 145 mm
d. None
164.The distance to be maintained while fixing axle pulley on wheel, from wheel hub to axle pulley outer wedge for 4.5 KW alternator is
a. 225 mm
b. 240 mm
c. 145 mm
d. None
165.‘V’ belt dropping/smoking/burning due to mechanical failure
a. Brake block jamming
b. Guide cups of damper’s have dropped
c. Both a and b d. None
166.‘V’ belt dropping/smoking/burning due to electrical failure
a. Load on Alt is heavy
b. Wrong alignment
c. Loose/excessive tension
d. All of the above
167.The minimum insulation resistance to be maintained for 4.5KW alternator is
a. 1 Mega ohm
b. 2 Mega ohm
c. 20 Mega ohm
d. None
168.The minimum insulation resistance to be maintained for 18, 22.75 & 25 KW alternators
a. 20 mega ohm
b. 2 Mega ohm
c. 5 Mega ohm
d. None
169.No. of ET’s used in 25 KW RR Unit MA type
a. 2
b. 1
c. Zero
d. None
170.No. of MA’s used in 25 KW MA type RR Unit
a. 2
b. 1
c. Zero
d. None
171.Width of grooved axle pulley of 4.5KW alternator is
a. 200mm
b. 190mm
c. 136mm
d. None
172.Width of grooved axle pulley of 18, 22.5, 25 KW alternator is
a. 200 mm
b. 190 mm
c. 136 mm
d. None
173.The type of suspension bushes are to be provided TL/AC alternators/ suspension bracket as per RDSO specification no RDSO / PE/Ac/0006/99 (Rev.0)
a. Cast nylon bushes
b. Nylon 66 bushes
c. MS bushes
d. All of the above
174.Residual magnetism lost in the alternator core the reason is
a. Field polarity changed
b. Alternator is in idle condition for long time
c. Both a and b
175.As per the Railway Board letter No. 2006/Elec(G)/138/3Pt. I unit Exchange spare recommended for alternators and Regulators for TL/AC depot
a. 5%
b. 10%
c. 15%
d. None
176 .ERRU stands for
a. Electronic Rectifier cum Regulator Unit
b. Electro magnetic Rectifier cum Regulator unit
c. Electrostatic Rectifier cum Regulator Unit
d. None
177. IGBT stands for
a. Insulated Gate By polar Transistor
b. Injection Gate By polar Transistor
c. Indicator gate By polar Transistor
d. None
178. IGBT is
a. Fast switching device
b. Slow switching device
c. Very fast switching device
d. None
179. The size of capacity of fuses to be provided for 25kW ERRU in phase circuit
a. 160A
b. 200A
c. 220A
d. None
180.UVC used in ERRU must be
a) Suitable to work with all capacities
b) Suitable to work with all makes
c) Both a and b
d) None
181.The battery charging current limit with 4.5kW ERRU is to be set at
a. 24A +/-2A
b. 12A +/- 2A
c. 36A +/- 2A
d. None
182.The battery charging current limit with 25kW ERRU when both alternators are paralleled is to be set at
a. 110A +/-5A
b. 220A +/- 5A
c. 220A +/- 10A
d. None
183.The battery charging current limit with 18kW ERRU when both alternators are paralleled is to be set at
a. 80A
b. 160A
c. 240A
d. None
184.OVP provided with ERRU, shall latch before output voltage reaches to
a. Surge voltage
b. Over voltage
c. Both a and b
d. None
185.The rating of field fuse provided in HMTD ERRU
a. 10A
b. 20A
c. 15A
d. None
186. Matched set of ‘V’ Belts means
a) One belt drive
b) More than one belt drive length with in specified limits
c) More than one belt drive length not in specified limits
d) None of the above
187. Number of V Belts required for SG non AC coach of TL alternator
a) 3
b) 4
c) 2
d) None
188. The cross section of V belt is shaped roughly like
a) Isosceles Trapezium
b) Rectangle
c) Square
d) None
189.The gauge used for checking groove angle of axle and alternator pulley is a) No go & go gauge b) Pitch length gauge
c) Section gauge
d) None
190.The gauge used for checking pitch length of V belt is
a) No go & go gauge
b) Pitch length gauge
c) Section gauge
d) None
191. Capacity of Alternator of Train lighting 110V DC BG coach
a) 3KW
b) 4.5KW
c) 25KW
d) 18KW
192.3 phase Bridge rectifier in R.R. box converts
a) AC to DC
b) DC to AC
c) Pulsating AC
d) None
193. Regulator controls
a) Field voltages
b) Field currents
c) DC output voltage
d) DC output current
e) All the above
194.Capacity of Phase fuse provided in 4.5kW R.R.Box
a) 35A HRC
b) 16A HRC
c) 6A HRC
d) 10A HRC
195.Capacity of Field fuse provided in the 4.5kW Rectifier cum Regulator box
a) 35A HRC
b) 6A HRC
c) 16 HRC
d) 10A HRC
196.Capacity of HRC fuse provided for negative circuit in Rotary junction box excluding alarm chain pulling indication light circuit.
a) 35A HRC
b) 16A HRC
c) 6A HRC
d) 10A HRC
197.Capacity of HRC fuses provided for positive circuit in RJB excluding alarm chain pulling indication light circuit.
a) 16A HRC
b) 35A HRC
c) 10A HRC
d) 6A HRC
198.Capacity of Limit switch provided for Alarm chain pulling indication light circuit is
a) 10A
b) 15A
c) 35A
d) 40A
199.Positive and Negative cables in roof run through on either side of coach to avoid.
a) Earth leakages
b) Over loads
c) Short circuits
d) None
200.Level of Illumination is measured by
a) Multimeter
b) Techno meter
c) Lux meter
d) Conductivity meter
201.Recommended level of minimum illumination to be attined in Second class compartment with F.T Fittings.
a) 30Lux
b) 40Lux
c) 16Lux
d) 60Lux
202. Recommended size of Aluminium cables for B +ve and B –ve in 110V coaches.
a) 16sqmm
b) 35sqmm
c) 4sqmm
d) 50sqmm
203.The wattage of TL Fan
a) 32W
b) 10W
c) 80W
d) 60W
204.The capacity of battery fuse for 110Volt SG TL coach is
a) 40A HRC
b) 16A HRC
c) 10A HRC
d) 4A HRC
205.The minimum clearance between the top of the battery and battery box for maintenance of cells shall have
a) 50mm
b) 150mm
c) 100mm
d) None
206.M.S.Rod/MS Flat provided in the battery boxes after loading cells. The purpose of M.S Rod/MS FLAT is
a) Anti theft arrangement
b) To strengthen the battery box
c) Not to drop batteries on run
d) All the above
207.Total number of mono block batteries for one set of 110V TL coach are .
a) 9
b) 12
c) 18
d) 54
208.The voltage of mono block battery of 110V coach is
a) 2V
b) 1.5V
c) 6V
d) 1V
209.Total voltage of one battery set (18 mono blocks or 54 cells) of 110V TL coach.
a) 24V
b) 108V
c) 120V
d) 110V
210.The insulation resistance of 110V coach when measured with 500V Megger during healthy weather condition.
a) 2 mega ohms
b) 1 mega ohms
c) 3 mega ohms
d) 0.5 mega ohms
211.The insulation resistance of 110V coach when measured with 500V Megger during adverse weather condition.
a) 2 mega ohms
b) 1 mega ohms
c) 3 mega ohms
d) None
212.Capacity of Rotary switches provided in Rotary junction box is
a) 40A
b) 16A
c) 10A
d) 15A
213. 204. NName of the meter used to measure Air velocity ( B )
a. Multi meter c. Thermometer
b. Anemometer d. Ammeter
214. Rating of Static inverter used in SG AC Coaches ( C)
a. 20 KVA c. 25 KVA
b. 35 KVA d. 22.75 VA
215. In regulator how many windings are available in Magnetic amplifier ( A&C)
a. 6 c. 4
b. 3 d. 5
216. Size of V belts used for 25KW Alternator ( C )
a. C121 c. C122
b. C123 d. C124
217. Name the meter used to measure relative humidity ( A)
a. PSYCROS meter c. Humidity meter
b. Multi meter d. Voltmeter
218. 1 ton of refrigeration is ( D )
a. 12 BTU c. 1200BTU
b. 120 BTU d. 12000 BTU
219. Thermostat Setting for WINTER used in AC coaches ( C )
A 19, 19, 21 c. 17, 19, 21
b. 22, 22, 24 d. 20, 21, 22
220. Calculate degree of Fahrenheit equivalent to – 40°C ( C )
a. 40°F c. – 40°F
b. – 20°F d. – 50°F
221. The gap between the two halves of axle pulley should be ( B )
a. 0.5 – 1.0 mm c. 3.0 – 4.0 mm
b. 2.0 – 3.0 mm d. 5.0 – 5.5 mm
222. Required level Torque Newton/meter to tightened the nuts and bolts OF Amar Raja cells (VRLA) connection ( C )
a. 10 c. 11
b. 12 d. 13
223. What are the AH capacity of cells used in AC coaches ( A )
a. 800, 1100 c. 120, 800
b. 500, 120 d. 120, 240
224. State the standing pressure of F – 12 refrigerant used for in AC coaches ( B )
a. 60 to 70 c. 70 to 80
b. 80 to 90 d. 50 to 60
225. Name of the Acid used in lead acid cells ( A )
a. Sulphuric Acid c. Nitric acid
b. Hydrochloric Acid d. Phosphoric Acid
226. Give the Spg & Voltage of Fully charged cells ( A)
a. 1220 & 2.2 c. 1200 & 2.2
b. 1220 & 2.1 d. 1200 & 2.1
227. Cut in speed for B/L alternator for 25KW Alternator ( D )
a. 17 KMPH c. 20KMPH
b. 19 KMPH d. 22 KMPH
228. Inverter converts ( A )
a. DC to AC c. AC to AC
b. DC to DC d. AC to DC
229. Function of SPP relay ( A )
a. Preventing single phasing c. Preventing shorting of phases
b. Both d. None
230. Function of proving relay ( B )
a. Ensure of starting of heater /compressor before blower c. Ensure of starting of compressor before blower
b. Ensure of starting of blower motor before compressor/heater d. Ensure of starting of liquid receiver.
231. Cooling thermostats setting (mercury thermostats) in I AC coach ( A )
a. 22, 24, 26 c. 17, 19, 21
b. 24, 24, 26 d. 19, 19, 21
232. IGBT are used as ( A )
a. High frequency switching device c. Low frequency switching device
b. Illuminating device d. Amplifier
233. Battery fuse rating in AC coaches is ( A )
a. 250 A c. 600 A
b. 400 A d. 200 A
234. No of regulators are available in I AC coaches ( A ) a. 1 c. 2 b. 3 d. 4
235. One RMPU AC coach is provided with how many compressors. ( A )
a. 4 No’s sealed compressor c. 4 No’s open type compressor
b. 2 No’s sealed compressor d. 2 No’s open type compressor
236. PSI is the unit of ( A )
a. Pressure c. Humidity
b. Temperature d. Velocity of gas
237. Boost charge of VRLA cells ( A)
a. 2.3 V/Cell c. 2.25 V/Cell
b. 110 V/Cell d. 115 V/Cell
238. Trickle charging of VRLA cell ( C )
a. 2.3 V/Cell c. 2.25 V/Cell
b. 110 V/Cell d. 115 V/Cell
239. No of MA’s in 25 KW regulators ( C )
a. 1 c. 2
b. 3 d. 4
240. No of ET’s in 25 KW regulators ( A )
a. 1 c. 2 b. 3 d. 4
241. Rectifier converts ( B )
a. DC to AC c. AC to AC
b. AC to DC d. DC to DC
242. HP cut out trips the compressor in Under Slung AC Coaches ( A )
a. 17.6 Kg/cm² c. 0.76 Kg/cm²
b. 7.6 Kg/cm² d. 76 Kg/cm²
243. LP cut out trips the compressor in Under Slung AC Coaches ( C )
a. 17.6 Kg/cm² c. 0.76 Kg/cm²
b. 7.6 Kg/cm² d. 76 Kg/cm²
244. Heater coil rating in I AC coaches is ( A )
a. 3 KW c. 4 KW
b. 5 KW d. 7 KW
245. Give the half load setting of R/R of 25 KW AC ( A)
a 95 c. 100
b 90 d. 85
246. Named the meter used to measure Vacuum ( A )
aMicron c. Picron
bTrivector d. Sicron
247. Give the diameter of Axle pulley used in AC coaches ( B )
a546.6 mm c. 500.6 mm
b572.6 mm d. 600.6 mm
248. Give the tension length of spring used in Tension rod of 25 KW Alternator ( A )
a 260 mm c. 269 mm
b 265 mm d. 275 mm
249. Why lead acid cells are called as Secondary cells ( C )
a Since it can’t be recharge c. Since it can be recharge
b Since it can’t charge initially d. None
250. What is Pre cooling ( A )
a Cooling of AC coach before placing on PF c. Cooling of AC coach while running
b Cooling of AC coach after starting the train d. None
251. Give the DC link voltage in static inverter ( B )
a 500 c. 400
b 600 d. 700
Write down the abbreviation.
1 PWM PULSE WIDTH MODULATED
2 VRLA VALVE REGULATED LEAD ACID
3 IGBT INSULATED GATE BIPOLAR TRANSISTOR
4 FRPCPY FAILURE RATE PERCENTAGE PER YEAR
5 BTU BRITISH THERMAL
UNIT II.
True of False
01. Expansion valve expands the gas irrespective of load (T / F) FALSE
02. M – 22 gas is used in RMPU’S (T / F) TRUE
03. Refrigerant requirement in U/S AC plant is approximate 27 Kg (T / F) FALSE
04. Refrigerant requirement in RMPU AC plant is approximate 15 Kg (T / F) FALSE
05. Vane relay ensured that blower motor has started before switching on compressor. (T / F) TRUE 06. TDR setting between 2 compressor of one RMPU is 10 Sec (T / F) FALSE
07. One coach (RMPU) is having 4 No’s of inverters (T / F) FALSE
08. BCK compressors are sealed compressor (T / F) TRUE
09. Manu rope compressors are sealed compressor (T / F) TRUE
10. ACCEL compressors are sealed compressor (T / F) FALSE
252. Function of cooling pilot relay ( A )
a Ensure the function of Compressor c. Ensure the function of heater
b Ensure the function of Compressor/Heater d. None of the above 65
OBJECTIVE TYPE.
1. The process of removing heat from low temperature level and rejecting at high temperature is called. REFRIGERATION
2. Any substances for change of its state at constant temperature absorbs/give up heat is called. LATENT HEAT
3. The sum of sensible heat and latent heat of substance in process is called ENTHALPY.
4 The latent heat of fusing ice is 144 BTU/LB
5. The unit of refrigeration is TON OF REFREGIRATION – 12000 Btu/Hr or 3023.98 K.Cal/Hr
6. The temperature measured by ordinary thermometer is called SENSIBLE HEAT of the temperature.
7. What is the boiling point of water 100 ◦C
8. AT what temperature water starts freezing_ 0 ◦C
9. One watt is 3.412 BTU.
10. One BTU is 0.252 K.calaries.
11. The unit of heat is BTU OR K.CAL
12. RMPU means ROOF MOUNTED PACKAGE UNIT
13. The setting of HP cutout in RMPU coaches is 415 psi
14. The setting of LP cutout in under slung coaches is 35 psi
15. The boiling point of refrigerant R22_ -40.8 ◦C
16. The boiling point of refrigerant R12. – 29.8 ◦C
17. Freezing point of refrigerant R22
18. R12 is being replace with R-134A in latest Refrigeration system.
19. The latent heat of evaporation IS THE HEAT REQUIRED TO CHANGE THE LIQUID INTO VAPOUR.
20. The temperature maintained in the refrigerator is LESS then 0 degree C.
21. The dry bulb and vet bulb temperatures equals then the RH is 100%
22. The moisture absorption in refrigeration circuit is done by DEHYDRATOR CUM FILTER
23. The commonly used refrigerants are R 12 & R 22
24. The lubrication of system in the sealed compressors is done by FREEZOL
QUESTION BANK FOR ELECTRICAL POWER MAINTENANCE
1. Layout of sub-station, maintenance
2. Transformer and its maintenance
3. Circuit breakers
4. House wiring and techniques
5. Underground cables
6. Motors
7. D.G sets
8. Pumps
9. Tariffs, power factor
10. Insulating materials 1
11. Regulations for power line crossings
TRANSFORMERS
1. What is the transformation ratio?
E2 = N2 = I1 E1 N1 I2 Where,
E2 = secondary voltage
E1 = primary voltage
N2 = no. Of secondary turns
N1 = no. Of primary turns
I2 = secondary current I
1 = primary current.
2. What is the E.M.F. equation of a transformer?
E1 = 4.44φmax fN1 volts
E2 = 4.44φmax fN1 volts Where,
φmax = maximum flux,
webers F = frequency, hertz
3. What are the fittings and accessories should be provided on a transformer?
The fittings and accessories of a transformer are:
1) Thermometer.
2) Silicagel breather.
3) Bottom valve.
4) Top valve.
5) HT and LT bushings.
6) Terminal Box.
7) Bucholz relay.
8) Conservator.
9) Tap changer.
10) Inspection covers.
11) Rating plate.
12) Oil and temperature indicator.
4. What is an auto transformer and what is its main advantage?
An auto transformer can be conceived of as conventional transformer with two windings, but secondary winding is connected in series with the primary windings. An auto transformer is smaller in size, lower cost, lower losses and high efficiency since the rating of the transformer is less than that of conventional two winding transformer for the same rated output.
5. What are the essential conditions for parallel operation of transformer?
a) They should have same polarity.
b) They should have same voltage ratio.
c) They should be of same percentage impedance.
d) They should be of same phase rotation for three phase transformers.
e) They should have identical vector diagram and phase displacement for three phase transformers.
6. What are the two basic types of instrument transformers?
They are
1. Current transformers.
2. Potential transformer. The secondary rating of Potential transformer is 110 volts and that for current transformer is 5 amperes, occasionally 100 volts and 1 ampere for PT and CT respectively may be available.
7. Why are transformers fitted with oil conservator?
The provision of conservator is to ensure that the transformer is completely filled with oil at all times, and to provide for the expansion and contraction of the oil due to temperature variations in the windings and minimum oil surface is exposed to the air.
8. What is the function of the breather?
Breather is provided on the transformer to prevent contamination of the transformer oil in the conservator, by the moisture present in the air entering the conservator. Generally breather is packed with silica gel crystals which has the property of absorbing all water vapour contained in the air passing through it, thereby making the air dry.
9. What is the function of a circuit breaker?
It has two functions:-
1) Protective function: During faulty/abnormal conditions without flash.
2) Controlling function: During normal conditions i,e, switching ON/OFF loads etc,. In oil circuit breakers, oil is the media to extinguish the arc developed during the operation of contacts and used for higher rating circuits.
10. What is the impedance voltage of transformer?
When impedance voltage is applied across one winding of a transformer it produces normal full load current to flow through secondary winding when its terminals are short circuited. It is 10% of the rated voltage and expressed as percentage of the applied voltage.
11. What is the efficiency of the transformer?
The efficiency of transformer is given by output divided by the input. = Output in watts X 100 / output in watts + Total losses in watts. The efficiency will be highest at a percentage load = 100 X square root of Iron loss / Copper loss.
12. Explain the regulation of transformer?
Regulation of transformer refers to the percentage voltage drop from no load to full load at unity power factor. In the larger sizes of transformers, the percentage regulation is of the order of 2 to 4 percent.
13. Briefly explain the maintenance schedule to be carried out on a transformer?
1. Hourly:
a. Load in Amps: Check against Rated figure and balance the load in 3 phases.
b. Voltage: Check against rated figure.
c. Temperature: Oil Temp and ambient Temp.
2. Daily:
a. Silica Gel: Check condition of silica gel and recondition / replace if required.
3. Monthly:
a. Conservation tank: check oil level and top up if necessary.
b. Humming sound: Check for abnormal humming of Transformer and attend.
c. Oil leakages: Check and attend the leakage on transformer body, conservator tank, oil drain valve radiators.
d. Tap changer switch: check for free movement of tap changer switch. Tap position to be clearly seen.
e. Connections: Check tightness. If loose tighten.
4. Quarterly:
a. Bushings: Check condition of bushings, clean the bushings.
5. Half yearly:
a. Non conservator transformer: check for moisture under cover and improve ventilation.
b. Cable boxes: check cable boxes (For indoor transformers)
c. Explosion vent diaphragm: check condition of explosion vent diaphragm. d. Gasket joints: check for oil leakage.
6. Yearly: a. Oil in Transformer: Check for
i. Dielectric strength.
ii. Water content
iii. Sludge
iv. Acidity
v. Dissolved gases
b. Earth resistance: Measure the earth resistance.
c. Relays, Alarm their circuits: Check functioning of relays, alarm & their circuit.
7. 2 yearly: Non conservator transformers: Internal inspection above core. Filter oil regardless of condition.
8. 5 yearly: Over all inspection including lifting of core and coils.
14. What is the function of Explosion vent? Explosion vent is provided for transformer this act as a pressure safety valve & burst in case excess pressure is developed in the transformer tank.
15. Explain the term Insulation resistance and the procedure for measurement of the same. Any electrical equipment can be operated at rated voltage / potentials. Hence it should be insulated according to potentials to give safety to the operator, so that potential to be zero on outer surfaces. The insulation resistance of equipment refers to the resistance between live/conducting part of equipment and earth. The insulation resistance can also be measured between two circuits separated by insulation. The IR can be measured by a Megger i.e., one terminal of megger is connected to conducting part and the other to the earth(or conducting circuit separated by insulation) and operate Megger and record the ohmic values on the scale which is from zero to few mega ohms.
16. What are the possible causes for the low insulation resistance, and their remedies?
Due to moisture – Joints should be tightened and in places where silica gel is provided should be replaced with pure blue colour. Due to Low BDV of Oil – New fresh filtered insulating oil with correct BDV is to be replaced. Due to defective Insulation tie rod – Correct insulation tie rod is to be provided. Insulators flash over – Insulators are to be cleaned periodically from dust and other foreign materials and cementation Part Earthing due to tracking. It should be cleaned properly. Due to oil deposits – Oil should be cleaned thoroughly with dry cloth.
17. Briefly explain the working of a diesel engine. The conversion of energy stored in a fuel can be considered in Two steps. In the first step, the fuel is burnt to release heat energy. In the second step, this heat energy is converted to mechanical energy. When the above two actions take place in two separate devices, the heat engine is known as an external combustion engine. Eg. Steam engines. When both actions, of burning fuel and conversion of energy, takes place inside the engine, the engine is known as an Internal combustion engine. Eg. Petrol and diesel engines used in Automobiles and pump sets etc., In such engines, the fuel is burnt within the engine and the resulting heat energy converted into mechanical energy.
18. Discuss the functions of the following system of a diesel engine
A) Fuel Injection system: The function of this system is to draw fuel from the fuel tank, clean it, raise its pressure and supply it in form of a high pressure spray at the proper moment in the cylinders.
B) Cooling System: Only a part of the heat energy of fuel is converted to mechanical energy in an engine. Due to very high temperature, the engine components gets heated. This continuous heating may cause some problems. In order to avoid such problems, the engine cylinders are continuously cooled. There are two types of cooling systems. Viz., Air cooling and water cooling.
C) Starving system: The crank shaft must be turned by some outside means for the first few cycles and after which it continuously runs . The types of starting systems are hand starter, Petrol engine starting, Compressed air motor starting. .
D) Lubricating system: There are many moving parts in an engine such as piston moving In a cylinder, two ends of connecting rod moving round piston and crank pins, crank shaft moving on its bearings etc., In order to reduce friction in these parts, they are to be lubricated. Lubricating oil is stored in the lower part of the engine and a pump delivers the oil to the different components needing lubrication.
19. List out the moving and stationary parts of a diesel engine. Cylinder block, Cylinder liners, Dry liners, Wet liners, Cylinder head, Head gaskets, Exhaust manifold, Crank shaft, Crank case, oil pan, piston, Expansion control,, piston head shoes, Piston rings, Oil control ring, piston pin, Connecting rod, Vibration damper, fly wheel, Main bearings, Valve actuating mechanism, Hydraulic valve lifter, Rocker arm, Cams and Camshaft, gears.
20. Explain the word ignition. Ignition system is to reduce a spark in the petrol engine cylinder, at the end of the compression stroke and to ignite the air fuel mixture.
21. Explain the objectives of lubrication and the parts that needs lubrication. When a body is in motion relative to other bodies, there is a force of friction between them, which opposes the motion and produces heat, resulting in wear of the metal surface. To reduce this friction and wear of the moving parts, Inter posing of some lubricating oil between the two surfaces.
a) Cylinder walls, Piston rings
b) Gudgeon pin (Small end of connecting rod)
c) Crank pin ( Big end of connecting rod)
d) Main crank shaft bearing
e) Timing gears
f) Crank shaft bearings
G) Valve mechanism
22. Discuss the checks to be made during the normal running of the engine
a) Fuel system
b) Lubricating system
c) Cooling system
d) Starting system
e) Exhaust system
f) Leaks of fuel, Water or Lubricating oil
g) Loose fastening
h) Unusual mechanical noise
i) Looseness of belt.
23. What are the maintenance records and how they are useful? What records are to be maintained for a D.G set?
The Maintenance records provide very useful information. By reference to these records, one can anticipate renewal or replacement of the components and can plan their stocking. Also the preventive maintenance schedules can be reviewed on the basis of such records. These records can also reveal weakness in the equipment, which can be corrected. For a D.G set the following records are to be maintained:
a) Cooling water inlet and outlet temperature
b) Exhaust temperature
c) Lubricating oil pressure, temperature
d) Generator voltage, current, frequency etc.,
e) Hours of operation
f) Fuel consumption
g) Lubricating oil consumption
h) KWH generated
i) Results of inspection and measurements on each Inspection.
j) Replacement of parts/components due to failure/wear and tear/breakdown.
24. How diesel engines are rated?
The manufacturers of diesel engines are Supposed to state the break power that their engine can develop at a given speed. This break power at a particular speed is known as its Rating, The break power can be expressed either in terms of Horse power of Kilo watts and speed is expressed in RPM. Max. Rating: It is the Horse power at a particular speed which the engine can develop for a short duration ie., 5 mts—30% Intermittent Rating: It is the Horsepower at a particular speed, which the engine can develop for about one hour---15% Continuous Rating: It is the Horse power at a particular speed which the engine develop with out interruption.
25. Discuss the importance of the preventive maintenance of a diesel engine. Components of an engine take wear and tear during their work. These components need periodical checking/servicing/replacement. To facilitate periodical checking/servicing/replacement of parts, periodical maintenance schedules are made. If such schedules followed strictly, the chances of unexpected maintenances are rare. The schedules as well planned maintenance is known as Preventive maintenance there by avoiding the break down of equipment and work interruption.
26. Explain the cleanliness of the diesel oil. The diesel engine fuel injection pump and fuel injector are having very close tolerance. If the diesel sent to these components is clear and chemically satisfactory, there will be very little wear of these components even after prolonged operating. However it may not be possible to obtain absolutely clean diesel fuel at the refineries. Hard and sharp foreign particles available in the oil cause accelerated wear of fuel injection system components. To minimize such damage due to fuel contamination, extreme care is required during installation of different fuel lines, for which a no. of filters, water separators are permitted.
27. What are the different checks to be carried out on D.G sets. What are the items to be checked in ‘A’. Check and explain the nature of check.
1. Lubricating Oil: Check the lubrication oil level in engine and governor and top up if necessary. Check the oil bath level.
2. Radiator water: Check radiator water level. Check oil bath cleaner oil level.
3. Air cleaner oil: Check the condition of pre-cleaner dust pan. Check the condition of air cleaner restrictions.
4. Fuel System: Check and record fuel oil. Drain sediment from Fuel Tank.
5. Battery: Clean the battery. Tight the connection.
6. Switch gear: Check automatic starting switch for its proper functioning. Clean the D.G Set.
7. D.G Set: Check the condition of belt for its proper tension. Observe Oil leakages. Observe abnormal sound. Record lub oil pressure Record Voltage Record Load Current Record KWH Meter reading.
28. What are the functions of starter? Ans. The functions of starter are:
(i) To start, and stop the motor
(ii) To limit the starting (or inrush) current, when necessary
(iii) To permit automatic speed control, when required, and
(iv) To protect the induction motor as well as the connected equipments from the sustained over-load, no-voltage, under-load, etc. Conditions.
29. How many types of 3-phase motors are there? There are two types of 3-phase motors:
(1) Squirrel cage rotor type
(2) Wound rotor type
30. What are the various starters used? Ans. Direct online starter and Star delta starter for squirrel cage induction motor. Rotor rheostat starter for slip ring induction motor.
31. Draw the internal connections of a DOL starter?
32. How many types of squirrel cage rotor are there?
There are two types of squirrel cage rotors:
(1) Single cage,
(2) Double cage
33. What is the formula for determining the synchronous speed and no. Of poles of an induction motor? Synchronous speed, Ns = 120f R.P.M. P And no. Of poles, P = 120f 75 Ns Where, f= frequency in hertz F=50Hz then: Ns=120 x 50 P =6000 R.P.M. P And P= 6000 Ns
34. Explain in brief the working principle of a 3-phase squirrel cage induction motor. On connecting the stator windings to a 3-phase source of supply, a 3-phase rotating magnetic field is developed in the stator. An e.m.f. is induced in the rotor bars due to which conduction of current is established in the bars which develops a torque and sets the rotor into rotation.
35. Explain in brief the working of a 3-phase slip-ring induction motor. The stator of a slip-ring induction motor is identical to a squirrel-cage induction motor’s stator. The rotor of this type of motor is wound like its stator. The no. Of poles and phases of rotor-windings are the same as of stator-winding. The 3 one side terminals of three rotor-windings are joined at one point to make a star-connection and the other 3 terminals connected to 3 slip-rings. These slip-rings are connected to an external 3-phase rheostat by means of 3 carbonbrushes. The external resistance is added to the rotor winding circuit for increasing the starting torque and decreasing the starting-current at the time of starting the motor as shown in the figure. As the motor attains its normal speed, the external resistance is cut gradually and finally the slip-rings get short-circuited. If the rotor resistors of a slip-ring induction motor are connected in delta then a parallel circuit will be formed. Then the total resistance will be smaller than their individual resistances. Rheostat-resistors connected in delta will not fulfil the condition of producing high starting torque. Therefore, the rheostat-resistors should be connected in star only. Wound-rotors are costlier than squirrel-cage rotors but their starting torque is much higher than that of squirrel-cage rotors.
36. Write the names of various single phase (φ) motors. The names of various single phase motors are follows:
(1) Split-phase (φ) motor,
(2) Capacitor motor (a)capacitor-start motor,(b)capacitor-run motor,(C) capacitor-start capacitor-run motor or double capacitor motor.
(3) Shaded pole motor
(4) Universal motor or A.C. series motor or AC/DC motor
(5) Repulsion motor –
(a) plain repulsion motor,
(b) repulsion-start induction-run motor,
(c) repulsion induction motor.
37. Why are the single phase (φ) induction motors not self-start?
Because of only one phase (φ) winding, there is no rotating magnetic field in a single phase induction motor. Since, the field has no rotating nature, hence, it is incapable to rotate the rotor and the motor can’t start by itself.
38. Draw a connection diagram of a capacitor-start induction motor.
39. Give the names of main parts of a capacitor start motor.
(1) Stator, made by joining together the slotted silicon-steel laminations.
(2)Running winding, which is made of copper wire and is fastened in the slots.
(3) Squirrel cage rotor, made by joining together the silicon-steel laminations.
(4) Centrifugal switch whose operating device is mounted on the shaft and the switch is fitted Inside a Bakelite box.
(5)Electrolytic capacitor fitted to the motor’s body.
(6) Bearings (ball or journal), both end-covers, terminal-plate.
40. What may be the possible causes if a motor starts with a difficulty of supplies a low torque? The possible causes may be as follows:
(1) Defective capacitor,
(2) Worn out bearings,
(3) Short-circuit in the starting or running winding,
(4) Loose rotor-shaft, (5) Wrong connections.
41. What may be the possible causes if a capacitor motor begins to emit smoke on starting?
(1) winding are short-circuited,
(2)Centrifugal switch fails to put ‘OFF’ the running winding,
(3) Bearings are worn out.
42. What are single –phase motors? Motors which operate on single phase supply and are of generally fractional horse power with a reading of less than 1 HP.
43. How would you reverse the direction of a rotation of a capacitor start-inductionrun motors? By reversing either the running or starting-winding leads where they are connected to the line. Both must not be reversed.
44. What is a universal motor? It is built like a series D.C motor with the difference that both the stator and armature are laminated. They can be used either on d.c or a.c.
45. What could be the reason if a split phase motor runs too slow? It could be due to starting winding being open or grounded or burnt out.
46. What are the various Starter used? DOL Starter, Star Delta starter, Rotor rheostat starter.
47. Enumerate the possible reason if a 3-phase motor fails to start? Any one of the following reasons could be responsible:
1. One or more fuses may be blown.
2. Voltage may be too low
3. The starting load may be too heavy
4. Worn bearing. 48. A motor stops after starting i.e. it fails to carry load. What could be the causes? Any one of the following: a. Hot bearing, which increase the lo
ad by excessive friction
b. Excessive tension on belt, which causes the bearing to heat.
c. Single phase on the running position of the starter.
49. What is meant by single phasing and what are it causes? By single phasing is meant the opening of one wire (or leg) of a three phase circuit.
50. What is jogging? It means inching a motor i.e. to make it move a little at a time by constant starting and stopping.
51. What are the maintenance schedule of motors? The following are the maintaining schedules. Occasionally Check motor for over heating. Terminal connection should be tightened, ventilation slot to be cleaned and kept free. Monthly Motors is dusty loactions. Blow out dust from windings. Quarterly Control equipment. Check for proper function. Correct for settings. Belts. Check belt tension. Excessive belt tension to be reduced. Loose belts to be adjusted. Brush holders& brushes of slip ring motors. Check for proper bedding of brushes. Align brush holder replace brushes if necessary. Half yearly Ball/roller bearings. Check foe sufficient grease. Make up grease if necessary. Avoid over greasing. Annual Winding of motors. Check for abrasion peeling or cracking or discolouration of insulation. Blow out the motor winding with clean dry air. Free ventilation holes. Insulation resistance. Check insulation resistance to earth & between phases of motors winding, control gear, etc.
52. What are the various protections provided for motors?
For human safety: Earthing of the motor frame
From Faults: HRC fuses. For protection against short circuit faults.
Overload relay for protection against overloads.
No volt coil for protection against low voltage/ No voltage.
Single phasing preventer for protection against single phasing. Circuit breakers
53. Name the different types of circuit breaker?
a) Bulk oil circuit breaker
b) Minimum oil circuit breaker
c) Air breaker circuit breaker
d) Sulphur hexa fluoride circuit breaker
e) Vaccum circuit breaker
f) Earth leakage circuit breaker
54. What is a circuit breaker? Circuit Breaker is a device capable of making and breaking a circuit under normal as well as under abnormal conditions.
55. Explain maintenance activities carried out on L.T switch gear/Bus bar?
a) Switch OFF panel board and blow out dirt through inside panel and switches.
b) Check & tighten terminals at the Bus bar & switches.
c) Check cable entry for provision of proper insulating bushes at bus bar & switches.
d) Check and clean pitted contacts, check for any overheating/flash marks and searches for causes.
e) Check and ensure proper earthing to bus bar and switches. Check and ensure bus bar neutral is rigidly earthed.
56. Define and discuss the following ratings of A.C circuit breaker a. Rated short circuit breaker current: The rated maximum interrupting current/breaking current is the RMS value of 3-phase current which can be interrupted supply by the circuit breaker under fault/short circuit occurred. The value of maximum breaking current given by the manufacturer should not be exceeded. This refers to the rupturing capacity of CB for breaking maximum short circuit current under fault/short circuit condition of safety (Rupturing capacity of CB is generally in MVA). Here safe interruption means that the time of interruption of CB should not exceed the rated interruption time of CB to avoid damage to the loads. At the same time CB should be able to withstand for the instantaneous over loads. b. Rated short circuit making current: The rated making current is the maximum RMS current against which the breaker is capable of closing and immediately opening without welding of contacts or any other damage.
57. Describe the following. 1. Temperature rise test: - In this test the rated current through all three phases of switchgear is passed continuously for a period till a steady state condition is achieved. Temperature rising at different points is measured and should not be more than 50 degrees centigrade under any circumstances.
2. Mill volt drop test:- This test is used to measure the contact resistance of whole of CB. The voltage drop across the breaker pole is measured for different values of dc current. The voltage drop gives a measure of resistance of current carrying part and contacts. The dc current should be more than 100 amps and less than rated current.
3. Insulation resistance measurement
4. Mechanical endurance tests:- A CB should open and close at the correct speed and perform such operations without mechanical failure. Hence the breaker mechanism is subjected to a mechanical endurance type test involving repeated opening and closing operations. Out of 1000 such operations, 50 Nos are to be operated by energizing the relay. It should work satisfactorily without failure and without requirement of adjustment to the operating mechanism. Then only it is considered that the CB is passed Mechanical endurance test.
5. No load mechanical tests:- Mechanical tests on High voltage CBs are conducted without current and voltage in the main circuit for 1000 no: of operations of opening and closing. There should not be any mechanical failure of contacts and mechanism. Out of 1000, 100 operations are done by connecting main circuit contacts in service with trip circuit. Then only it is considered that CB is passed under this test.
6. Routine test :- Once a particular design is found satisfactory, a large number of similar circuit breakers are manufactured for marketing. Every CB is then tested before putting in service. These tests are known as Routine tests.
7.Type test :- Any equipment when designed to certain specification and is fabricated needs testing for its performance. The general design is tried/tested and the results of such tests conducted on one selected breaker and are thus applicable to all others of identical construction. These tests are called type tests.
EARTHING
58. What is the object of earthing? The object of earthing system is to provide a surface under and around a station, which shall be at a uniform potential (nearly zero or absolute earth potential). This earth surface should be as nearly as possible to the system. This is in order to ensure that, all parts of apparatus other than live parts and attending personnel shall be at earth potential at all times.
59. What are the advantages of earthing? Reduced operation & Maintenance cost Reduction in magnitude of transient over voltages. Improved lighting protection. Simplification of ground fault location. Improved system and equipment fault protection. Improved service reliability. Greater safety for personnel & equipment. Prompt and consistent operation of protective devices during earth fault.
60. What is an earth Electrode? It is a metal pipe, rod or other conductor which makes an effective connection with the general mass of the earth.
61. Name the equipment used for measuring Insulation resistance and Earth resistance and the units? Insulation resistance – Insulation megger, units – Mega ohms. Earth resistance-Earth megger, units – ohms.
62. Give the maximum Earth resistance value? Large power station - 0.5 Ω Major power station - 1.0 Ω Small substation - 2.0 Ω In all other cases - 8.0 Ω
63. What are the factors affecting earth resistance? The resistance of earth system depends upon the following factors:
1. Condition of soil
2. Temperature of soil
3. Moisture content of soil
4. Size and spacing of earth electrodes
5. Depth, at which the electrode is embedded
6. Material of conductor
7. Quality of coal, dust, charcoal and salt in the earth electrode pit 8. No. of electrodes connected in parallel
64. What are the methods of improving earth resistance? The earth resistance can be considerably reduced by digging around the earth electrode to a depth of 1.5 or 1 meters, cleaning the surface of the earth plate or pipe of rust, filling with charcoal soaked in salt solution.
65. Why is Earthing of electrical apparatus necessary? It is well known that the metallic frames of all electrical equipments should be solidly connected to earth to drain away the faulty current (Earth leakage) quickly so that fuse will be blown or Circuit breaker is tripped and to keep the frame at earth potential to achieve safety to the equipment as well as the staff.
66. Enumerate the checks to be carried out on Earth connections? Half Yearly check list:
1. Earth wire joints: Check for proper continuity.
2. Earth clamp bolts & nuts in earth pit: Check for proper contact of earth clamps, slackness, rust & dirt.
3. Earth pit: Check for general condition including dryness.
4. Earth resistance: HT installations: Measure the eath resistance the values shall be main earth 1 ohm and isolated earth 8 ohm. Earth pit no, earth resistance value and date shall be painted on vertical surface of earth pits. Annual Check list :
1. Earth Resistance: LT installations: Measure earth resistance the values shall be main earth 1 ohm and Isolated earth 8 ohm. Earth Pit No, Earth Resistance value and date shall be painted on vertical surface of earth pits.
2. Earth Pits : Check up the electrode for proper earth continuity.
67. Explain the procedure for Measurement of Earth Resistance by 3 point method? By a portable megger earth tester: In making measurements under this method, the terminals P1 and C1 of the instrument are strapped together and connected to the spike (electrode) under test. The terminals P2 and C2 are connected to two auxiliary spikes driven at spacing large enough not to cause mutual interference between the fields of the different electrodes. The depth of insertion of these spikes must not exceed onetwentieth (1/20) of their spacing distance. The megger reading gives directly the electrode resistance.
MEGGER EARTH TESTER C P POTENTIAL SPIKE CURRENT SPIKE EARTH ELECTRODE E E Sub-station
68. Draw the lay –out diagram of a 11kV/440V sub-station ?
69. Name the various electrical equipments available in a sub-station?
1. Transformer
2. Isolator
3.Lightening anester
4. Bus-bar panel 5. Circuit breaker
6. D.G Set
7. Battery charger 500kV A
70. What are the various details to be entered in a sub-station log book? HT.Side
1.Voltage
2. Current
3.Power factor LT.Side
1. Voltage
2. Current
3. Temperature reading of transformer
4. D.G.Set operting voltage and current, time of operation, temperature
5. Shut down
6. Failures & attention to faults
71. What are the safety items to be available in sub-station.
1. Sand bucket with sand.
2. Fire extinguishers.
3. First Aid Box with medicine.
4. Artificial respiration chart.
5. Ladders.
6. Safety earthing chains.
7. ‘Men working’ caution boards.
8. ‘Danger’ caution Boards.
9. Safety Helmets.
10. Safety belts.
72. Describe briefly the purpose of each of the following in Electrical Sub-Station.
i) Lightning Arrestors: A lightning arrestor is a device which protects transformer and for other electrical Apparatus from an over load of electrical voltage. This overload can occur either because of lightning or improper switching in the circuit. The lightning arrestor provides a path over which the overload can pass to the ground before it has a chance to attack and seriously damage the transformer or other equipment
ii) Shielding wire: Its main function is to provide shielding to the transmission line conductors and low height towers against direct strokes of lightning. The shield wire / ground wire increases the potential of the conductor and reduce the surge stress on the insulator due to its capacity coupling.
iii) Metal (Ballast) in substation yard: It is used as a safety measure Due to metal (Ballast) spread in the substation, hazards and deterioration of equipment on account of stagnation of water is reduced. The growth of grass is considerably reduced
73. Name the functions of the following in a sub-station.
(i) Potential Transformers: Potential transformer is used to measure the high voltages in a substation in conjunction with standard low range voltmeters, It also facilitate to operate relays or pilot lights whose ratings are very low. These transformers are extremely accurate ratio step down transformers. (ii) Current Transformers: These transformers are used with low range ammeters to measure currents in high voltage ac circuits. In addition to insulating the instruments from the high voltage line they step down the currents. (The range of the ammeter is increased) in a known ratio.
(iii) Batteries: Batteries are used in a sub-station for feeding supply to control, protection and indication circuits. They are also used for operation of circuit breakers and interrupters and motor operated isolators. They are also used in remote control centre.
(iv) Isolators with Earthing heels: These are used for making and breaking a circuit in off load. The isolators are designed to operate without load. The isolators having an Earthing arrangement such that in the event of opening/switching off a circuit breaker one of the circuit is earthed automatically which is also an additional safety aspect.
74. Write the five essential steps involved in effecting shut down. Before issuing permit –to-work in writing to the official-in-charge of the working party, the Authorized official shall personally effect the shutdown. The procedure involves 5 essential steps as detailed below.
(a) First step:- Identify the electrical circuits feeding the equipment or the area concerned remembering the possibility of alternative feeds as in the case of parallel feeders or different supplies such as AC 3-phase,4-wire bunglow supply mains, 230 volts street lighting mains, pump control mains etc., running on the same alignment or in close proximity to each other.
(b) Second step:- Cut off the supply to the circuit or areas required by opening the concerned control switches. In case of AC 400 volts, 3-phase,4-wire circuits or 3-wire circuits, the neutral link should be opened, as this is liable to assume a potential above earth under certain conditions.
(c) Third step:- To prevent the lines being re-charged inadvertently, the switch concerned should able locked in the ‘OFF’ position, or where there is not possible the control fuses in the switch should be removed and kept under lock and key by the authorized official. In the case of circuit breakers, they should be racked out and locked, the key being retained under the personnel custody of the Authorised Official. Lastly a “men at work” Caution Board should be hung up on the switch or circuit breaker concerned.
(d) Fourth Step:- To ensure that the supply has been correctly cut off, each and every conductor should be tested for supply by means of a testing device. In the case of 400 volts,3-phase,4-wire AC lines, two lamps of equal wattage connected in series shall be used. The testing device should be checked on a live line, before and after the test, to ensure that its indications are reliable.
(e) Fifth step:- Finally, to ensure safety under all conditions, the dead lines including the neutral conductor should be solidly earthed, by means of an approved Earthing clamp or flexible wire having sufficient section. This should be done on both sides of the point where work is to be carried out.
75. What are the items to be checked on 2 /4 / 6 pole structure. Briefly mention the nature of checks to be carried out on the structure?
1. Structure :
a. Check for leaning.
b. Check for any birds nests- Remove if any
c. Paint the structure once in 5 years (Last done date)
2. Anticlimbing Device: Check and ensure availability
3. HT Danger board: Check and ensure availability
4.Insulator: Check of chipped / cracked insulator.
5. Jumpers:
a. Check the condition for oxidation and flash marks & for strands cut.
b. Check and ensure provision fo standard PVC insulation sleeves for all Jumpers.
6. Lighting Arrestor: Check the condition for flash over marks/ cracks.
7. Bird guard lacing: Check the condition.
8. Earth connections: Check for the condition of earth connections for:
i. Structure
ii. Lighting Arrestor(Ensure connections to separate Earth pit)
iii. AB switches and also to its operating handle.
iv. Transformer body and neutral (Double earth with 4 SWG GI wire or flat)
9. A.B. switches:
i. Check for oxidation of contacts of AB switches. ii. Check the locking arrangements and attend.
10. H.T. Fuses: Check the condition and ensure proper rating of standard fuse element is used.
11. Spare HT cable: Check the condition of spare HT cable and cable termination. Spare cable should be suitably supported and terminals to be earthed.
12. APDISCOM Supply point: Check the APDISCOM structure, Metering Cubicle and report to APDISCOM officials if any defect is noticed.
76. What are the different types of insulators used in OH lines? Pin insulator, shackel insulator, stay insulator, reel insulator.
77. Explain the maintenance checks to be carried out on O.H line.
1. Posts : Check the alignment for lean posts. Ensure trimming of infringing tree branches.
2. Cross arms and stay clamps : Check the condition of cross arms, stay clamps and ensure for proper fixing and for proper spacing. Bird Nest if any on cross arms shall be removed.
3. Overhead lines and guarding wire: Check the overhead lines, guarding wires for sag and ensure tightness.
4. Insulators : Check all insulators for cracks and clean thoroughly.
5. Jumpers: Check and clean all the Jumper connection at incoming, out going, tapping point’s and at cut point’s and ensure tightness. Check the condition of jumpers
(1) For oxidation and flash marks.
(2) For strands cuts.
6. Earth Connection : Check and clean all the earth connections and ensure for tightness and continuity, and also ensure all the cut point posts, stays are earthed. Measure and record the individual and combined earth resistance values.
7. Stay Arrangements: Check the studs and stay arrangements and ensure for proper fixing of clamping and for load tension.
8. Conductor: Check it for cut in stands and damage of conductor.
9. Service tapping: Check and ensure proper connections of service tapings. Check and ensure proper Tension in Service Tapings.
78. During maintenance what items are to be checked on U.G cables.
1. Check the insulation values of cables once in a year.
2. Check underground cables near the poles / structure for any damages and also the condition of vertical protection pipe.
3. Check for proper earthing of cable armored and cable protection pipe.
79. What are the maintenance aspects to be taken care of oil used in transformer?
1. Oil level should be checked at frequent intervals the cause of any serious loss of oil investigated. 2. All leaks should be repaired as quickly as possible
3. Oil for topping up should comply with relevant standard specification preferably it should be from the same source as original oil. Samples of the oil should be taken at regular intervals and tested for dielectric strength, acidity and crackle records of these together with top oil temp, should be kept. 80. What is meant by power factor in A.C. circuit?
(a) The ratio of real power to the apparent power is called power factor. Power factor = Real power Apparent power
(b) Power factor is the cosine of angle between voltage and current. P.F. = Cos ᶲ
(c) The ratio of resistance to the impedance is called P.F. P.F. = resistance Impedance
81. What are the disadvantages of low P.F.? The following are the disadvantages of low power factor. 1. As the apparent power increases for a given power load at a constant voltage, the line current increases. This again causes increased voltage drop in the line and thus decrease in terminal voltage across the load.
2. Due to reduced voltage, the induction motor will accelerates slowly and will take higher current to compensate for the load torque.
3. Due to decreased voltage, the heat output of electrical furnaces, heaters reduces
4. The under grounded insulated cables are heated more and thus insulation is weakened.
5. The capacity of switch gears and fuses must be increased,
6. The transmission line drop increases and efficiency goes down.
7. Output of the incandescent lamp decreases.
82. What are the regulations of power line crossings for electrified territory? and Explain the procedure of modifying power line crossings in case of new electrification of tracks between Railways and State Government. These regulations apply to Electrical Over head lines and on under ground Cables crossing Railway Track.
- An Over head line crossing shall normally be at right angles to the Railway track. In special cases, a deviation up to 30 degrees may be permitted. More than 30 degrees deviation requires approval from the Electrical Inspectorate of the Railways.
- The steel structure shall normally be galvanized in accordance with IS:2629 – 1966.
- The minimum distance of the structure (supporting the crossing span) from the centre of the nearest Railway track shall be equal to the height of the structure in meters above ground level plus 6 meters. In special circumstances, the Electrical Inspectorate may permit a lesser distance being adopted subject to any conditions, he deemed fit.
- The crossing span shall be restricted to 300 meters or 80% of the normal span for which the structures are designed, which ever is less.
- The factor of safety of all structures, conductors, guards, guys and ground wires used in the crossing shall be as stipulated in the Indian Electricity Rules 1956 (as amended in November 1984). An over head line crossing over the Railway track already shall be located at the middle of over head equipment span supported by two adjacent structures/traction masts. The distance between any of the crossing conductors and the nearest traction mast or structure under the most adverse conditions shall not be less than 6 meters.
- No over head line crossing shall be located over a Booster transformer, Traction switching station, Traction Sub-station or a track cabin area location in the electrified area.
- The working of a Railway crane under over head line crossing shall normally be avoided. The minimum height above rail level to the lowest portion of any conductor of a crossing including guard wire under the conditions of maximum sag shall be as follows:
1. UPTO AND INCLUDING 11 KV NORMALLY BY CABLE
2. ABOVE 11 KV AND UPTP 66 KV 14.10 METERS
3. ABOVE 66 KV AND UPTP 132 KV 14.60 METERS
4. ABOVE 132 KV AND UPTP 220 KV 15.40 METERS
5. ABOVE 220 KV AND UPTP 400 KV 17.90 METERS
6. ABOVE 400 KV AND UPTP 500 KV 19.30 METERS
7. ABOVE 500 KV AND UPTP 800 KV 23.40 METERS
The minimum safe clearance between the height of a a crane jig highest point and lower crossing conductor shall be as under;
NORMAL SYSTEM MIN. SAFELEARENCE VOLTAGE IM METERS 33 KV--- --- --- ---
1.50 66 KV--- --- --- --- 2.00 110 KV --- --- --- 2.25 132 KV --- --- --- 2.50 220 KV --- --- --- 3.50 400 KV --- --- --- 6.00 500 KV --- --- --- 7.25 800 KV --- --- --- 11.50
- A Double set of strain insulators shall be used in cross span.
- The supporting structure of the over head line crossing on Railway land shall be provided with anti climbing device.
- Each structure on either side of the crossing span supporting the transmission /distribution line conductors shall be earthed efficiently by two separate distinct earths and connections
PROCESSOF POWER LINE CROSSINGS ON RAILWAY TRACK:
- Data, design, Calculations and drawings of the crossing are to be submitted to Railway by the SEB’s through the divisional officers.
- An agreement is to be carried out between them.
- Railways will check the feasibility and advise to SEB’s the acceptance and probable date of execution of the work in consultations with the traffic control.
- SEB’s should make all the necessary arrangements at the work spot to complete the work in the minimum possible time
- On the day of the execution, Traffic and power blocks will be taken by the Railways and after taking the necessary safety precautions, they will permit the SEB’s to start the work and to complete the work in the least time duly taking the necessary safety precautions.
- After completion of the work, the SEB’s will return the permit to work and then after satisfying the conditions, Railways will cancel the traffic and power block.
- A certificate of completion is to be submitted to the Railways by the SEB’s.
- Railways will check all the work in accordance with the drawings and other parameters. And after satisfied, they will give the permission to charge the line.
- The crossings will be charged in the presence of a Railways.
- The supervisory charges at the rate of Rupees one lakh per hour or part there of will be charged from the SEB’s.
83. What is meant by low, medium, high and extra high voltages?
- --Low : <250V
- --Medium : >250V but <650V
- --High : >650V but < 33000V
- --Extra high : >33000V
84. How the Vertical and Horizontal clearances of power line crossings are to be measured. Explain permissible limits of vertical clearances up to 132KV EHT power line crossings?
The horizontal clearances can be measured by means of measuring tape i.e., between the centre of track and nearest mast/pole/tower on both the sides of the track. It can also be measured by a second span of the power line crossings on both sides of the track. Vertical clearances can be measured between centre of the conductor and ground by providing a plumb off with Rope at the centre of the conductor of the power line crossing/guarding.
85. What are the different types of wiring adopted for house hold wiring? Shich system is now adopted in Indian Railways?
1. Cleat wiring
2.Caring and copping
3. Conduct wiring
4. Metal sheathed wiring
5.CTS or tough rubber sheathed
6. Mineral insulated wiring
7. Now in Indian Railways casing and copper conduit wiring is employed.
86. What are the Classification of insulators? Sl.No. Class Max. Safe temp Description of insulation 1. 2. 3. 4. 5. 6. 7. Y(Formerly 0) A E B F H C 90◦C 105◦C 120◦C 130◦C 155◦C 180◦C Above180◦C The insulation of this class consists of materials such as cotton, silk, paper with out impregnation, etc. Class A insulation consists of materials such as cotton, silk, paper immersed with oil, etc. The insulation of this class consists of materials of better quality than Class A materials such as leatheroid, paper, empire cloth, fibre, etc. Class B insulation consists of materials such as mica, glass fibre, asbestos, etc. The insulation of this class consists of materials of better quality than Class B insulation, The insulation of this group consists of materials such as silicone elastomer, and combinations of materials such as mica, glass fibre, asbestos, etc. Class C consists of materials, such as mica, porcelain, glass, quartz, etc.
87. Name the parts of a fuse Ans. Fuse wire, Fuse carriers, Fuse Carrier Contacts, Fuse Base, Fixed Contacts. 88. Why should we separate power & light circuit? Ans. Power circuits are separated from lighting circuits due to the following reasons:
(i) Faults such as over loadings, short circuits, etc. Commonly occur on power circuits which can cause unwanted disturbances to lighting circuits if they are connected on the same supply mains.
(ii) Power circuits are designed for more voltage drop than lighting circuits which reduces the illumination output of the lamp.
(iii) The life of the lamp decreases with much fluctuation of voltage on the line.
89. Explain the the Insulation resistance test between conductors and between conductor and earth in a wiring installation? Draw a rough diagram?
Ans. Before performing the insulation resistance test of complete installation, the main switch should be put off, all the fuses should be intact in the distribution box, and the lamps (i.e. load) and all the switches should be put ON. One terminal of the megger is connected to the earth wire of the supply or to a water pipe and the other terminal (L) of the megger is connected to one live wire and together with the neutral of the circuit as shown in Fig. Then the handle of the meggar is rotated at its normal speed and the reading on the scale is noted. This reading is the insulation resistance between the conductors and the earth. If the needle of the meggar shows zero reading, it means that there is a direct connection between the conductors and the earth and that should be removed before conducting the next test. The reading of the megger should not be less than 50 /no. Of outlets. In general 1MΩ insulation resistance may be considered as sufficient for the complete installation. Insulation Test between Conductors: This test is conducted to find the value of the insulation resistance between live and neutral conductors and also to locate a short circuit if any in the complete installation. The wire connected during the previous test should be removed with the fuse terminal together with neutral link as shown in Fig. All the lamps should be removed and the main switch should be put OFF. All the fuses should be intact and all the switches should be ON. The megger terminals should be connected across the two main fuse terminals of the installation. The handle of the meggar should be turned at normal speed. In this test also the result should not be less than 1MΩ. This is the insulation resistance between live and neutral conductors. However if the reading is zero, it means there is a short circuit in the wiring which should be removed. This test should be performed only if the result of the last test is found satisfactory. If there is any fault in the first test, that must be removed. QuestionPaper.Org 92 90. What should be the height of the following: (1) Single pole switch, (2) Wall socket, (3) Batten wiring (4) Ceiling fan, (5) Power wall socket Ans.(1) 1.5 metres. (2)1.5 metres (3) 2.3 metres (4) 2.75 metres (5) 0.33 metres 93. What tests are to be conducted a) while a wiring is in progress b) After wiring is completed? a) While house wiring is in progress 1) Continuity test of wiring. 2) Testing of polarity of single pole switches. 3) Insulation resistance test between conductors. b) After wiring is completed. 1) Insulation resistance test to earth. 2) Earth resistance test. 94. What should be the rating of megger used for measure I.R of circuit? The minimum voltage rating= 2x rated circuit voltage ex. For house wiring, Voltage rating of D.C megger=2x 250V=500V DC 95. What is the allowable min insulation resistance of house wiring? One mega ohm. Pumps 96. What are the different types of pumps used in Railways? The different types of pumps used in Railways are, Submersible pumps Jet pumps Centrifugal pumps Mono-bloc pumps Rotary pumps Mono-sub pumps 97. What are the main problems experienced during operation of a centrifugal pump? Pump not starting. No liquid delivered. Not enough liquid delivered. Pump discharge pressure islow. Pump looses prime after starting. Pump overloads driver. Excessive vibration. Bearing overheat. Bearing wears rapidly. 98. Describe the constructional features of centrifugal pumps. The centrifugal pump consists of the following main parts. QuestionPaper.Org 93 1. Bed plate: This may be of cast iron or welded steel which has provision for passing of dowel locating pins driven through the pump and motor legs for easy assembly and correct alignment. 2. Pump Casing: It is made of cast iron and may be split horizontally to enable removal of the impeller and spindle. 3. Impeller: This is made up of close grained cast iron or cast steel . to eliminate rusting, impellers are made of gun metal. They are hydraulically and dynamically balanced. 4. Spindle: This is made of steel. To reduce the leakages, hurts collars, gun metal sleeves and bronze neck rings are used. 5. Stuffing Box and Gland Packing: This serves two purposes – on the suction side it prevents leakage of air and on the delivery side leakage of water under pressure. It has gland bolts, packing material. 6. Bearings: These may be of ball, roller or sleeve type. 99. Explain the working of centrifugal pump. The working of centrifugal pump is based on the principle of centrifugal force. Hence it is named as centrifugal pump. This type of pump in its simplest form comprises an impeller rotating in a volute casing so that liquid/water entered into the centre of impeller and discharged at the periphery resulting into development of vacuum on suction side and more water/liquid flows into the impeller and constant discharges can be obtained. Priming is very important for centrifugal pump to avoid entry of air in the system due to centrifugal force. 100. What maintenance checks are carried out in pump? Quarterly check Pump noise Pipe connections and nut/bolts Foot valve strainer Moving parts for lubrication Yearly check Remove impeller, replace if vanes are worn out totally Replace shaft sleeves, if worn out Replace gland packing, if worn out Replace any other worn out part Replace mechanical seal if damaged. 101. What are the precautions you take while installing. (a) Submersible pump: Motor of the submersible pump to be filled up with adequate quantity of clear, cold water before coupling to the pump and ash should not enter. b) Pump set should not be lowered to the bottom most point of bore well. c) It should be lowered up to the above mud level only. d) Proper coupling between each GI pipe and pump sets should be ensured. e) Avoid cable joints and bents. f) Provision of Water level guard should be fixed at the coupling between motor and pump. QuestionPaper.Org 94 g) The gap at the mouth of the bore well around submersible pump should be closed. h) Supporting clamps should be mounted properly. (b) Horizontal Centrifugal pumps: a) Foundation and foundation bolts for pump and motor should be ensured as per the specification. b) Proper alignment between motor and pump should be ensured. c) Proper functioning of non return valve should be ensured. d) Anchoring of suction pipe and priming of pump should be ensured. e) Lubricating bearing and tightness of gland packing should be ensured. 102. What are the functions of the following in a pumping installation. (a) Strainer: It is fixed in the suction side which prevents the entry of foreign matter in the system. (b) Foot Valve: It is fixed at the bottom of the suction pipe which is useful to maintain liquid in the suction pipe while in operation and stationary conditions. Entry of foreign matter in the pumping system can be prevented by providing a suitable mesh around the foot valve. The foot valve has a hinged leather faced flap which lifts up during the normal operation, and drops and closes the opening when pump stops. (c) Sluice valve: It is provided in the discharge pipe line which is used at the time of replacement of pumps. In normal operations this should be kept opened. This is generally provided where a pump is installed below the water level in a reservoir which gives positive feed in to the pump. (d) Non-return valve: This should be of robust design and strong enough to withstand the heavy shocks caused by water hammer action, when the pump is shut down, and protects centrifugal pump and the foot valve. This valve is provided in the delivery side of the pipe line. (e) Vacuum and pressure gauges: Vacuum gauge is used to measure the pressure below that of atmospheric pressure either in feet or lbs/inch. Pipe connection to the gauge is taken from the suction inlet to the pump pressure gauge is provided on the delivery side of the pump to measure out put water pressure of the pump. 103. Describe the merits and demerits of submersible pumps over vertical shaft pumps. Submersible pump can be installed in the bore wells which are not exotically vertical where as vertical shaft pumps cannot be installed in such cases. 2) The installation of a vertical pump requires the services of an experienced mechanic since alignment of column pipe and rotating shaft should be very accurate. 3) In case of oil lubricated vertical pump special attention is required and maintenance cost is also more than submersible pump. 4) Submersible pumps are more reliable than vertical shaft pumps which has got various mechanical elements. 5) Submersible pumps can be operated by remote control very easily. 6) Dry running of the submersible pump leads to burning of motor. 104. What are the basic criteria for selection of (i) Submersible QuestionPaper.Org 95 pumps (ii) Vertical shaft pumps. Criteria for pumps selection is : 1. Nature of liquid, water (Raw or tread) or chemicals to be handled. 2. Type of duty required i.e., whether continuous, intermittent or cyclic 3. Present and projected demands and pattern of change in demand. 4. The details of head and flow rate required 5. Type and duration of the availability of the power supply 6. Selecting the operating speed of the pump and suitable drive/driving gears. 7. The efficiency of pumps and consequent influence on power consumption and the running costs 8. Possible permutations of the parameters of the pumping system, in lading capacity and number of pumps (With standby) combining them in series or in parallel 9. Options of different modes of installations and their influence on the civil and structural costs, on the case of operation and maintenance and on over all economics. 105. Indicate the type of pumps you select in the following application duly justifying your selection. i. Bore well pump for individual domestic water needs = Submersible pump for more depths and jet pumps for less depth. ii. Open well near river beds for water supply to colonies, industrial and commercial needs of high suction lift =Multi stage Centrifugal pumps iii. Bore well pumps at small Railway premises = Submersible pumps iv. Open well pump with suction lift of 5 M for Divisional HQ Railway premises = Monoblock pump v. Pump for Transfer of HSD oil from drums to Engine tank = Rotary pump 106. i. Name important data to be collected for designing pumping installations. ii. Calculate the Rating of pump motor, used for pumping 120 G.P.M. of water against total head of 212 feet? Assume efficiency of pump as 70%. Maximum daily consumption of water for the present and anticipated increase consumption for the next five years for domestic, commercial, industrial use on the base of yardsticks approved. On the above basis hourly requirement can be calculated and curve can be drawn. Type of fluid to be pumped Type of source in reservoir / sump, well (Including depth) etc., and then hydraulic data recorded during the last 15 to 20 years. Location and capacity of Overhead tank can be derived from the above points. Route and diameter of the pipe line by considering the utilization for different places and various types. Times of requirements. Power supply availability Sanction for provision of stand by prime movers. ii. Ans. QuestionPaper.Org 96 Total Head = 212 feet Water to be pumped = 120 GPM Therefore Work done required = 120 x 10 x 212 (10lb/gallon) Efficiency= 70% HP= 120 x 10 x 212/0.7 x 33000 = 11 HP. 107. Briefly explain the Daily and Half yearly checks to be carried out on mono bloc pumps. Daily Maintenance: 1. Gland Packing: Leakage through Gland packing. 2. Bearings: Bearing temperature 3. Sound: Whether any under noise or vibration is present. 4. Readings: Pressure, Voltage and current reading. Half Yearly Maintenance: 1. Free movement of gland of the stuffing box. 2. Cleaning and oiling of the gland-bolts. 3. Inspection of packing and repacking if necessary. 4. Alignment of the pump and the drive. 5. Cleaning of oil-lubricated bearings and replenishing fresh oil. If bearings are greaselubricated, the condition of the grease should be checked and replaced to correct quantity, if necessary. 6. An anti-friction bearing should have its housing so packed with grease, that the void spaces in the bearings and the housing be 1/3 to ½ filled with grease. A fully packed housing will cause the bearing to overheat and will result reduced life of the pump. TARRIF 108. What is Tariff? Name the different categories of Tariff under which power are obtained from distribution authorities? Electrical Tariff represents the basis on which charges are recovered from the consumers for supply of electricity. The main objectives of the tariff is to distribute equitably the cost of supplying electrical energy among the various classification of use such as lighting, heating, industrial and, bulk supply etc. The different kinds of tariff in common use are as under: Simple tariff Flat rate tariff Block rate tariff Two part tariff Max. demand tariff Power factor tariff Three part tariff Off peak tariff 109. (a) Explain (i) Load factor (ii) Diversity factor. LOAD FACTOR: The load factor is specified with its period viz., daily load factor, monthly load factor or annual load factor. QuestionPaper.Org 97 The annual load factor is defined as the ratio of KWH supplied by the station in a year divided by the product of peak load and 8760 (The no. of hours in a year). Yearly load factor: No. of units supplied in a year --------------------------------- Max. No. of units which can be supplied = No of units supplied in a year --------------------------------- Max. Demand X 8760 Similarly monthly load factor = KWH supplied in a month --------------------------------- Max. Demand X 24 X 30 The value of load factor is always less than 1. The no. of units supplied can be obtained from the summation curve and the max. Demand on half hourly basis or 15 minutes basis can also be obtained from the summation curve explained earlier. Higher load factor means more no of units generated per year. DIVERSITY FACTOR: The diversity factor is defined as the ratio of the sum Of maximum demand of the power stations. Diversity factor: Sum of Max. Demands of each category ------------------------------------------ Max. Demand of the station. The value of diversity factor is always more than 1. The greater the diversity factor, the lesser will be the Max. Demand. Hence the supply organizations try to improve the load factor as well as the diversity factor by inducing the customers to use the electricity during off peak time and they may be charged at lower rates for such schemes. (b) Find the monthly load factor of a sub-station with a M.D. of 5 MVA and average monthly consumption 25,00,000 units. Average P.F. = 0.8. Monthly load factor: KWH supplied in a month ------------------------------- Max. demand X 24 X 30 = 25,00,000/5 x 10 X 10 X 10 X 24 X 30 X 0.8 = 125/14.4 = 0.86 110. The following are the features of HT. category tariff. a. M.D. 80% of CMD or RMD whichever is more. b. M.D. (Penalty) If the RMD exceeds 110% for portion exceeding CMD, MD charges are double the normal MD charges. QuestionPaper.Org 98 c. Energy charges. Recorded energy units or 250 units for kVA of CMD whichever is more. d. P.F. penalty 2 Paise / Unit if the P.F. is below 0.9. e. P.F. discount 1 Paise/unit if the P.F. is above 0.95. f. Meter rent Rs. 1500/- g. MD charges. 1500 / KVA, Energy charges Rs. 420/KWH. Find the energy bill if the joint readings are as follows for 11 kV substation having CMD: 2500 kVA. (a) M.D. = 1200 kVA, KWH=6,00,000 units P.F. = 0.96. i. MD = 80% of CMD = 80% of 2500 = 2000KVA MD = 80 % of RMD = 80% of 1200 = 960 KVA ii. MD penalty = No penalty as RMD is less than CMD MD charges = Rs 1500 x 2000KVA =Rs30,00,000 iii. Energy charges Recorded energy units=6,00,000xRs420= Rs25,20,00,000 is less. 250 units/KVA of CMD=250x2500KVA = 6,25,000 units. 6,25,000 x RS 420 =Rs 26,25,00,000 is more. Power factor penalty =Nil P F discount =1paise/unit x 6,25,000 =Rs 6,250. BILL: Rs 30,00,000+26,25,00,000+1500-6250 = Rs26,54,95,250.Ans. FIRE SAFETY 111. What are the reasons for fire occurrence Enumerate in : 1. Substations:- Due to leakage/spillage of oil from oil drums, Paints and other inflammables etc coming in contact with electrical sparks of burnt switches, cables, short circuit of wiring etc, Anybody throwing a lighted cigarette on the oil drum or used cotton waste causes fire in substation. Flashover from switches, circuit breakers, etc also leads to fire in substations. 112. Why at all a Fire occur At workshop:- i) Improper storing of inflammables like petrol, Diesel, Paints etc and if anybody throws a lighted cigarette on these items or due to electrical short circuit, overheating and burning of cables etc fire occurs. ii) If used cotton waste/oil cotton waste etc are not disposed off properly and any welding arc, grinding material fire, cigarette fire comes in contact with the cotton waste leads to fire. iii) Electrical short circuits, burning of cables etc leads to fire in workshops. At AC /TL coach :- i) Carrying inflammables in the coaches and getting lit by cigarette etc results in fire. ii) Carrying of intoxicated drinks/liquor which when QuestionPaper.Org 99 comes into contact with spark, etc leads to fire. iii) Smoking and throwing the lighted butts etc on the easily combustible material by the passengers will also lead to fire in coaches. iv) Some times unsafe use of stoves in pantry cars leads to fire. v) Using of oversize fuses, under size cables, improper/loose terminal connections, tightness of connections, etc leads to fire in coaches vi) Bypassing of safety items like fuses, relays etc, low insulation resistance causing earth leakage, also leads to fire in coaches. At residence:- i) Leakage of gas cylinder, stove, improper storing of inflammables like petrol, kerosene, diesel etc which can come in contact with sparks or fire. Electric heater when come in contact with clothes, ii) Electrical short circuit, burning of wiring etc leads to fire. iii) Lighted cigarette, beedi etc falling on huts, beds or other Combustible material stored in the residence leads to fire . At office.:- i) Electrical short circuits, burning of cables/wires, etc leads to fire. ii) At the time of burning of old records/papers in unsafe manner and due to wind flow the flames come in contact with combustible material and cause spread of fire. 113. How many types of fire extinguishers are available in your jurisdiction. There are four types of fire extinguishers A class: Soda ash cartridges, water buckets, chemical foam, Halon gasses etc., B class: Chemical foam, Dry powder, carbon dioxide Halon gas C class: Dry chemical powder, carbon dioxide, Halon gas D class: Halon gas, Dry chemical powder, carbon dioxide 114. Classify various types of fires and how do you extinguish them in detail. There are four types of fires classified. They are A type : General fires such as solid materials, cotton, wood etc. B type: Oil fires such as Liquid materials, oil, grease etc. C type: Chemical fires such as fires in gasses D type: Electrical fires such as metallic, electrical etc. For extinguishing the fire use the above mentioned fire extinguishers as mentioned according to their classification in answer ‘G’. 115. Write 5 slogans for (1) Prevention of fire (2) Prevention of accident. Prevention of fire:- i) No Smoking. ii) Do not over load the Electrical equipment iii) Handle carefully the inflammables. iv) No loose connections and Hanging wires. QuestionPaper.Org 100 v) Do not bring naked flame near a battery. Prevention of accident:- i) Be cautious. ii) Handle with care. iii) don’t play with electricity. iv) Don’t lean on switchboards and electrical equipment. v) Use safety items viz., safety belts, helmets etc 116. What are the preventive measures to be taken to avoid Fire accidents in Workshop. ---Use electrical equipments of approved design and from reputed manufacturer. ---They are to be installed properly, by experienced staff who are fully aware of their responsibilities and conversant with the statutory rules like IE rules and regulations for safe working on electric equipments. ---The electrical equipment has to be maintained properly by carryings out periodical inspections and tests to ensure that the equipment is safe. --- The equipment has to be used carefully, taking normal precautions . --- The place of working should be dry and free from inflammable items. ---proper earthing of the equipments is to be done. ---Loose connections and shortcut methods are to be avoided. Hanging wires and bare wires should not be allowed. 117. What action you will take when fire occurs in a HT Sub-Station? First isolate the substation. Switch off all the equipments. Use the fire extinguishers available in substation for extinguishing the fire Send the information to the nearest fire station Inform to the higher official Clear the combustible material if any near the vicinity of the fire. 118. Name the different types of cable jointing kits available. Ans. i. Heat shrinkable jointing kit. ii. Cold shrinkable jointing kit. Iii. Tapex tape type jointing kit. iv. Push on type jointing kit. v. Cast resin jointing kit. 119. On completion of laying, terminating UG cables what are the points to be noted down? Ans. On completion of laying, terminating and jointing of the cables, a plan should be prepared, which should contain the following details of the installation. a. Type of cables, cross-section area, rated voltage. Details of construction, cable number and drum number. b. Year and month of laying. c. Actual length between joint-to-joint or end. d. Location of cables and joints in relation to certain fixed reference points, for example, buildings, hydrant, boundary stones, etc. QuestionPaper.Org 101 e. Name of the jointer who carried the jointing work. f. Date of making joint. g. Results of original electrical measurements and testing on cable installation. All subsequent changes in the cable plan should also be entered. 120. Explain the maintenance procedure on underground cables? The maintenance of cable installation includes inspection, routine checking of current loading, maintenance and care of all cables and end terminations. INSPECTION When ever the cables or joints are accessible as in manholes, ducts, distribution pillars etc., periodical inspection should be made so that timely repairs can be made before the cables or joints actually cause interruption to service. Preventive maintenance in the form of regular inspection of all digging operations by other utilities or persons, carried out in areas they are electric cables exists is of utmost importance. CHECKING OF CURRENT LOADING The life of paper insulated cables is considerably reduced through overloading. It is, therefore, essential to check the loads as frequently as possible to ensure that the cables are not loaded beyond the safe current carrying capacities. The derating factors due to grouping of several cables, higher ambient ground temperature and higher thermal resistivity of soil, should not be neglected. MAINTENANCE OF CABLES Repairs of cables generally involve replacement of a section of the defective cable by a length of new cable and insertion of two straight joints. All repairs and new joint in connection with repairs should be made in the same manner as joints on new cables. In some cases where the insulation has not been damaged severely, or where moisture has not obtained ingress into the insulation, it may only be necessary to install a joint at the point of cable failure. MAINTENANCE OF END TERMINATIONS Visual inspection of all the cable end termination should be carried out regularly for any over heating flashing mark, insulation damage etc. Cable end terminations should be checked for tightness with a suitable torque wrench/spanner periodically. Check the cable support clamps, glands for proper position and intactness. 121. What are the points to be attended during POH of battery chargers? Ans. PERIODIC OVERHAULING OF BATTERY CHARGERS (Yearly) 1. Dismantle side covers, top covers. 2. Blow jet dry compressed air to remove dust and dirt. QuestionPaper.Org 102 3. Inspect the condition of transformer assembly, rectifier assembly, fuse assembly and wiring. 4. Check condition of bus bar heat sink, main diodes. Replace if found damaged/defective. The polarity of silicon diode must be checked before replacement of new diode. 5. Check the condition of transformer winding and other electrical parameter. If the transformer is found defective, take for rewinding. 6. Check the condition of rotary switches, push buttons. Clean and attend them for minor repairs. Replace with new one if found burnt/defective. The terminals of the rotary switch should be kept tightened. 7. Check all fuses and replace with new one if found defective. 8. Remove and clean thoroughly terminal board assembly. Replace components with new one if found damaged/defective. 9. Check the tapping of the transformer and attend damaged portion. 10. Replace burnt-out/defective wires/cables of terminal board. 11. Remove the Ammeter, Voltmeter and send it to test room for overhauling and calibration. 12. Check all joints and connections of primary and secondary winding. 13. Check the insulation and earth resistance of the charger. 14. Paint the control panel, if required. 15. Check the electrical parameters such as voltage, current, temperature rise and record. Also check the performance of the equipment for 4 hours. 122. Enumerate the likely causes for the main fuse blowing out in a battery charging rectifier? Ans. 1. Main fuse blowing out a. Power rectifier diode may be short circuited. b. Wiring may be short circuited. c. Winding may be short/low insulation. Check diodes and replace. Check & rectify. Check the resistance of winding and repair if required. QuestionPaper.Org 103 123. What are the different types of welding plants? Ans. The different types of welding plants are: Arc welding plants,CO2 and plasma welding plants. 124. What will happen if a motor is started with two phases only because of one fuse being blown off? Ans. The motor will not start. 125. What data should be noted while rewinding a motor? Ans. Before starting rewinding, the complete data of the motor should be noted. The data can be divided into two parts: (i) Name plate data: Note down the following details: Make of the motor, No. of phases, Horse power, R.P.M., Voltage, Full-load current, Frequency, Temperature, etc. (ii) Re-winding data: Note down the following details: No. of coils, No. of slots, Turns per coil, No. of coils per group, No. of groups, No. of poles, Coil-pitch, size of wire, No. of parallel paths, No. of conductors in each coil, Connections, Insulation used in slots, Insulation used on coils etc. 126. Name the energy efficient measures adopted in lighting? Ans. i. Use of CFL lamps. ii. Use of T5 fittings iii. Use of LED type fittings. iv. Use of work spot lighting. v. Using of Star rated lamps. 127. What are the advantages of an electronic choke as compared to normal choke? Ans. The advantages are as follows: i. It doesn’t produce any noise and doesn’t blink also. ii. It doesn’t consume more electric power. It saves 33% of electric power. iii. It doesn’t require a choke and a capacitor iv. It starts the tube in less than 1 second. QuestionPaper.Org 104 v. Its weight is low. vi. The choke circuit component can easily be repaired up. vii. It can work on voltage between 100 to 300 volts. viii. It doesn’t get hot. ix. Its life is double. x. It can work on A.C./D.C. source. xi. It gives more light. 128. What is the function of a choke in the florescent lamp? Ans. i. when the starter’s contacts get open due gas glow then the flux of the choke falls rapidly and a surge voltage of about 1000V is developed. The gas discharge glow is started in the tube at this high voltage. ii. when the tube is glowing then it supplies about 110volts to the tube. iii. it regulates the current at a stable rate during operation of the tube. QuestionPaper.Org 105 OBJECTIVE TYPE QUESTIONS ON ELECTRICAL POWER MAINTENANCE 1. The net resistance of a circuit consists of 4 resistances 1,2,3,4 in series is ___________________. 2. The net resistance of a circuit consists of 4 resistances 1,2,3,4 in parallel is ______________ a. 0.58 b. 0.48 c. 0.40 d. 0.50 3. The best conductor of electricity is a. Silver b. Aluminum c. Brass d. Zinc 4. The mercury is a _____________ conductor. a. Solid b. Liquid c. Gaseous d. None of the above 5. Dry air is a a. Conductor b. Insulator c. Semi- conductor d. None of the above 6. The theoretical water column that can be supported by atmosphere at sea level is a. 10 feet b. 24 feet c. 34 feet d. None of the above 7. In centrifugal pump water is admitted into the a. Center of rotor b. Outer periphery of pump c. None of the above 8. In a turbine pump the water enters into the pump from a. Center of rotor b. Outside opening on the casing c. None of the above 9. Which of the following pump require priming a. Centrifugal pump b. Turbine pump c. Submersible pump 10. In a submersible pump the motor is located a. Below the pump b. Above the pump c. In the middle QuestionPaper.Org 106 11. In a centrifugal pump water is a. Permitted to enter into the unit and circulate between rotor and stator b. Not Permitted to enter into the unit and circulate between rotor and stator 12. The bearings in a submersible pump are a. Water lubricated b. Oil lubricated c. Grease lubricated 13. Equipment earthing means a. Earthing of all metal work of electrical equipment other than live parts b. Earthing of all metal work of electrical equipment including live parts 14. System earthing is done to a. Limit the potential of live conductors with earth b. Increase the potential of live conductors with earth c. Decrease the potential of live conductors with earth d. None of the above 15. The meaning of earthing or grounding is to connect the earth point of equipment to general mass of earth by wire of a. Negligible resistance b. Higher resistance c. Low resistance d. None of the above 16. The minimum size of G.I pipe electrode used in pipe earthing is a. 25 mm Dia b. 40 mm Dia c. 50 mm Dia d. 70 mm Dia 17. The minimum distance of earth electrode from a building shall be a. 1.5 m b. 0.5 m c. 2.5 m d. 2.0 m 18. The maximum permissible earth ‘R’ values for major power stations is a. 0.5 b. 1.0 c. 2.0 d. 8.0 19. Earth continuity inside an installer from earth plate to any point in the installation is a. 1.0 b. 2.0 c. 3.0 d. 4.0 20. In maintenance free earthing the electrode is of_________. QuestionPaper.Org 107 21. The earthing electrode shall always be placed in a. Vertical position b. Horizontal position c. Any position 22. The minimum size of earth wire is a circuit / sub-circuit should be a. Equal to size of conductor used in circuit/sub-circuit b. More than the size of conductor used in circuit/sub-circuit c. Half of the size of conductor used in circuit/sub-circuit 23. The minimum no. of earth for earthing a transformer separate a. Two independent earth b. One earth c. Three separate & individual earth 24. The distance between two earth electrodes shall be a. Equal to length & earth electrode b. Twice the length & earth electrode c. No distance need to be maintained 25. The earth resistance should be checked once in a year a. On a dry day during dry season b. On a dry day during wet season c. Can be checked anytime 26. The minimum distance to be maintained between the two electrodes of earth megger when taking reading shall be a. 20 feet b. 40 feet c. 10 feet d. 75 feet 27. While measuring the earth resistance a. It is necessary to disconnect the electrode under test from the installation b. It is not necessary to disconnect the electrode under test from the installation c. Inter connect all the earth electrodes in vicinity 28. The combined Earth resistance of 33kV/11kV receiving station should not exceed a) 1 ohm b) 2 ohms c) 10 ohms d) 20 ohms 29. The combined earth resistance of 11kV/415 V Sub-station should not exceed a) 0.5 ohm b) 2 ohms c) 10 ohms d) 20 ohms 30. As per the present Tariff the minimum power factor of sub-station should be a) 0.8 b) 0.85 c) 0.90 d) 0.95 QuestionPaper.Org 108 31.The minimum clearance of lowest conductor from the ground of 33kV lines, across the road a) 3M b) 4M c) 6.1M d) 14 M 32. The minimum clearance of lowest conductor from the ground of 33 kv lines, along a street a) 5.8 M b) 4.0 M c) 3.0 M d) 14 M 33. The minimum vertical clearance from 11 KV line to any part of building a)2.0 M b)10 M c) 3.7 M d) 6.0 M 34. The minimum Horizontal clearance of 11 kV lines from any buildings a) 1.2 M b) 3.7 M c) 6.1 M d) 10 M 35. The Rod gap on the L.V. side of 11 kV/415V, 250 kVA Transformer is a) 300 mm. b) 100 mm. c) 50 mm d) Rod gap L.A. is not provided for LV side of Transformer 36. The rated voltage of L.A. for 11 kV/415V Transformer protection is a) 11 KV b) 12 KV c)9 KV d) 24 KV 37. For medium sized 11kV/415v, 500 kVA Transformer sub-station, the type of L.A. used are a) Station type b) Line type c) Distribution type d) None of these 38. The line type L.A. used for our 11 kV and 33 kV sub-station are having a standard normal discharge current (peak) a) 5 KA b) 10 KA c) 1.5 KA d) 2.5 KA QuestionPaper.Org 109 39. The span of supports for 11 kV over head lines should not exceed a) 100 m. b) 65 m. c) 30 m. d) 27 m. 40. Minimum insulation value of transformer of 11 kV / 415 V with 1000 V megger a. 200 mega ohm b. 10 mega ohm c. 50 mega ohm d. 100 mega ohm 41. Extra high voltage is more than a. 250 V b. 650 V c. 33 kV d. more than 33 kV 42. Speed of induction motor depends upon a. No. of poles b. Frequency of power supply c. Both a & b d. None of the above 43. Ceiling fan is a _____________ a. Single phase capacitor start & capacitor run motor b. single phase capacitor start motor only c. 3 phase motor d. None of the above 44. In a 11kV / 415 V sub-station the transformer is connected in _______________ to step down voltage. a. Star – star b. Delta – delta c. Star – delta d. Delta - star 45. The reason of drawing high current at the time of starting by an induction- motor is: a) high voltage b) low power factor c) zero back e.m.f. 46. In a three phase induction-motor, the speed of rotor is always lesser than that of stator. 47. A D.O.L. starter is used with squirrel-cage induction-motors up to 5H.P. 48. A star-delta starter is used with slip-ring induction-motors of 5 to 20 H.P. 49. A universal D.C. motor is a series motor. a) shunt b) series c) compound QuestionPaper.Org 110 50. If two transformers have different voltage ratios and their parallel operation is desired then: a) they can not work. b) they will work at different power factors. c) they cannot work on load. 51.In a transformer, the mutual flux links from: a) primary winding b) secondary winding c) both the windings. 52. For a small transformer, the 3-phase connections in use are: a) star-delta b)delta-star c)star-star 53._________ connection combination is used at a sub station to step-down the voltage ? a) star-delta b)delta-star c) star-star 54. The silica jelly used in the breather of a transformer stops the moisture to reach the insulating oil. a) rain water b) dry air c) moisture 55. If the pump fails to start the likely cause/s is /are a.) Fuses blown. b). Short circuiting. C). Heavy load on the pump d. )All of the above. 55. A delta-star connected 3-phase transformer is used for high voltage transmission. 56. The distance between two earth-pits should be _____________ 57. At ________ distance an earth-point should be installed from a building. 58. 1 horse-power (H.P.) is equal to _______watts. 59. The power consumption of a 100 watts lamp used 10 hour daily will be: a) 2 units b) 1 unit c) ½ unit d) 5 units 60.Commutator converts A.C. into D.C. 61. In a self-excited generator residual magnetism is necessary for producing the induced e.m.f. 62. The commutator is made of copper metal. 63. A D.C. shunt generator is used for battery charging purposes. 64. A D.C. over compound generator is useful for transmitting electrical power up to distant places. QuestionPaper.Org 111 65. A series motor is always started on load. 66. A starter protects a motor against he damages caused by a heavy current flow. 67. If the field or armature terminals of a d.c. shunt motor reversed then the direction of armature‘s rotation will change. 68._____________ Is the frequency of main-supply in our country. 69.1 µF is equal to a) 10-6F b) 106F c) 10-3F d)103 F 70. 11 kv HT Power supply is to be availed when the total load exceeds a. 100 KW b. 1000KW c. 75KW d. 56KW 71. The voltage of 11 KV supply is a. 11000V b. 1000V c. 100V d. 33000V 72. The EHT power line crossing means. a. Above 11KV b. Above 33KV c. Above 132KV d. Above 400KV 73. Guarding is required for the power line crossings of following Voltages. a. Up to 11KV b. Up to 33KV c. Up to 132KV d. Above 132KV 74. Tracks not likely to be electrified in the foreseeable feature come under category of (a) Category ‘A’ (b) Category ‘B’ (c) Category ‘C’ (d) Category ‘D’ 74.Radiator is used for cooling of diesel engine. 75. Power in the diesel engine is the ratio of work to time. 76. Diesel engine overhauling is recommended after every 25000 working hours. 77.Governor in a diesel engine is used for maintaining the given speed by adjusting fuel supply at various loads. 78.Vibration dampers are used for controlling the tort ional vibration of the crankshaft 79.Air filters are classified as dry type and oil type. 80.Unit of work in MKS system is Joule . 81.Carburetor is used for vaporizing petrol and mix it with air. 82.BEE is acronym for Bureau of Energy Efficiency. 83.The Electricity act 2003 has come into effect on 10.6.02. 84.RLDC stands for Regional Load Despatch Centre. 85.The requisition for shut down is submitted on form No.EE243. 86.The requisition for permit to work is submitted on form No.EE244. QuestionPaper.Org 112 87.Certificate for clearing shut down is issued on form No.EE245. 88.Competency Certificate ‘_C_’ is issued by SSE for skilled electrical staff. 89.The currency of Competency Certificate ‘C’ is 5 years. 90. The size of wire should be used as earthing-wire in house-wiring is ________________. 91.A. 7/20 size cable contains ____wires each of_______. 92. In diesel engines _________________ is compressed inside the cylinder. 93. In diesel engines the ______________ is injected which burns itself due to high temperature of compressed __________________. 94. Besides the use of D.G sets as a standby power supply arrangement they are also used in _________ in Railways. 95. During priming of pump __________________ valve is kept open to permit air to escape from the pump section. 96. In a centrifugal pump air leakage may take place either in ____________ or in ________________. 97. _________________ is provided in cable to avoid mechanical injury to the cable. 98. The different types of power cables classified on the basis of insulation used are ______________, ______________, _____________. 99. The minimum size of copper plate electrode used in earthing is -----------------. 100. The minimum size of galvanised iron and steel plate electrode used in earthing is ------ ----------- 101. The minimum size of G.I pipe electrode used in earthing----------- . 102. The minimum clear space required in front of switch board is___________ metre. 103. The minimum height of fencing to protect outdoor sub-station is _________metre. 104. The capacity of water storage tank with efficient standby pump should ______ of the maximum water consumption in 24hrs. 105. The capacity of water storage tank without standby pump should ______ of the maximum water consumption in 24hrs. 106. The output capacity of pump should be capable of supplying in _______ the normal quantity of water required in 24hrs. 107.Minimum clearance between highest traction conductor and lowest crossing conductor for OH Crossing voltage between 132 KV and 220 KV is 15.4 m 108. Minimum horizontal distance between power line crossing tower and track shall be Height of the tower + 6 m 109. Power line crossing tower should be earthed with an earthing electrode (T / F) TRUE 110. Guarding wire is not required if the system voltage of power line crossing is above 33 KV. 111.Jointing is permitted in the crossing span (T / F). FALSE 112. Inside station limits for B.G. line minimum height above rail of lowest crossing 113. Conductor for system voltages above 66 KV and upto 132 KV at mid span is 14.6 m 114. 11 KV crossing can be overhead type (T / F) FALSE QuestionPaper.Org 113 115. If crossing is provided with a guarding, a minimum clearance of _2.0 m shall be maintained between the bottom of the guard wire and highest traction conductor. Objective Type: Sl.No Item To be filled 1. Transformer Secondary Volts = Primary Volts x ( ) Primary turns. Secondary Turns (Primary Amps. Secondary. Amps. Secondary turns). 3. Breather is packed with material Silica gel (Silica Jel, Oil) 20 KV 4. The minimum BDV of transformer Oil is 40 KV (40 KV, 50KV, 55 KV) 5. Maximum permissible resistance of major substation 1.0 (1, 2, 8) 6. Maximum permissible resistance of small substation. 2.0 (1, 2, 8) 7. Earth fault relays providing against Earth fault (Earth fault, Core heating full of oil level) 8. Over current relays providing against Over current (over current. Over voltage Earth fault. 9. Low Voltage is not exceeding 250 V (250V, 650V, 33 KV) 10. Medium Voltage is not exceeding 650 V (250V,650V, 33 KV) 11. High Voltage is not exceeding 33 KV (250V, 650V, 33 KV and more than 33 KV) 12. Extra High Voltage is more than More than 33 KV (250V,650V, 33 KV and more than 33 KV) 13. MCCB is ---------- case circuit breaker. Moulded Miniature, Moulded). QuestionPaper.Org 114 QUESTION BANK FOR OFFICIAL LANGUAGE 1. When an employee is deemed to possess proficiency in Hindi? The employee is deemed to be proficiency in Hindi a)If he has passed Metric or equivalent or higher examination with Hindi as medium b) If he took Hindi as an elective subject in a Degree or Equivalent or higher examination c) If he declares that he possess proficiency in Hindi 2. When an employee is deemed to have acquired working knowledge of Hindi? An employee is deemed to have acquired working knowledge of Hindi a) if he has passed Metric or equivalent or higher examination with Hindi as subject b) if he has passed Pragya examination under government’s Hindi teaching c) Other examinations specified by the government d) if he declares that he has acquired a working knowledge of Hindi 3. What are different steps taken by Railways to implement Hindi in official work? As per article 342 (1) of the constitution, Hindi in Devanagari script will be the official language of the union. Article 343 (2) gives the president, powers to authorize the use of Hindi in addition to English. Under this power, president laid down some orders in 1952. Later, it was decided to continue using English and the official language act of 1963 was passed. This act was amended in 1967 to incorporate the assurances of Prime minister that English will continue to be used by a state for its communication with union till that state likes. In 1976, some more rules were framed under the official language rules like dividing the union into three regions for implementing the official language and incentives are introduced for using Hindi in official use, passing of Hindi examinations and others. 4. What incentives are given for passing various Hindi examinations? Passing of Prabodh --- Rs.250/- Praveen --- Rs.250/- Pragya --- Rs.300/- Hindi Typewriting --- Rs.150/- Hindi Stenography --- Rs.300/- Other Hindi examinationsConducted by voluntary bodies --- Rs.300/- Those passed with 60% or above will be given an increment. Special casual leave may be granted for appearing to such examinations. QuestionPaper.Org 115 5. What are the various incentives for use of Rajabhasha? ` 1. Awards for writing books on professional subjects in Hindi --- First prize is Rs.6000/- 2. Railway ministers best essay awards given during the Railway week First prize—Rs.1000/- Second prize – Rs.700/- 3.Group Awards to staff of a department who makes maximum use of Hindi – First prize – Rs.5000/- Second prize – Rs.3000/- Third prize – Rs.2000/-. Each employee gets Rs. 100/- 4. Boards individual Awards to employees for their work in Hindi –Rs. 850 and a certificate of merit given by Railway Minister (w.e.f.1987) 5. G.M’s individual Awards to employees – Rs.300/- and a certificate of merit 6. Awards of noting and drafting in Hindi First prize – Rs.800/- Second prize – Rs.400/- Third prize – Rs.300/- (w.e.f.1-4-98) 7. Incentive to typists and stenographers who in addition to their work in English, do Hindi typing and stenography work, a monthly allowances of Rs. 80/- to typists, and Rs.120/- to stenographers (w.e.f.1-8-97) 8. Two Awards of Rs. 100/- each to officers giving in Hindi in various Railway offices (w.e.f.1-4-98) 6. Translate into Hindi. (i) Memorandum ii) Service Register (iii)Confidential Report (iv)Please speak (v) Widow complimentary pass (vi) Urgency (vii) Increment (viii)Scale of pay (ix) Industrial Relations (x) Seniority List (xi) Honorarium (xii) Gazette Notification (xiii) Fixation of Pay (xiv) Official Language (xv) Nominee
(xvii) Notification
(xviii)Oath of Allegiance
(xix) Personnel Department
(xx) Periodical Medical Examinatio
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