APCPDCL: 2010
1. Merz-prise protection is used for Stator inter turn faults.
2. Lightning arrestor is installed near to Transformer.
3. In CE amplifier current gain is nealy High. (Nearly 500).
4. Which heating is used for non ferrous metals.—Indirect Arc furnace.
5. Which type of welding is used for Aluminium Alloys – Tungsten Arc Welding.
6. Units for luminous flux is
a) Lumen b) Lux c) Candela d) All
7. Value of Absolute Permittivity is 8.854 X 10-12 F/m
8. Which is the highest efficient generating station – Hydel power plant.
9. How was the DC chopper input and Output – Continuous and discontinuous.
10. When will be the DC motor output is maximum.
Back EMF is equal to the half of the supply voltage.
11. If one of the phases of synchronous motor phase is shorted then
I put the answer is Refuse to start.
12. When speed is increased the speed of the shunt motor is – Reduced slightly.
13. Which generator is used for Welding purpose – Differential compound generator.
14. In a series motor torque is proportional to before coming to the saturation.- Tse α I 2se
15. In a locomotive illumination purpose which type of battery is used?
I don’t know exactly but I put the answer is Lead-Cadmium cell or Nickel – cadmium cell
16. Kando system is referred in traction is 1-Ф to 3-Ф AC system.
17. Main line speed time curve is Trapezoidal speed time curve.
18. Water hammer effect can be reduced by constructing the Surge Tanks in hydero power systems.
19. Q = Charge, V= Voltage, E= Energy then Relation between them is E = QV.
20. In a shunt motor supply voltage is 250V, Shunt resistance is 200Ω , supply current is 200 A , then Armature current is 18.75A
21. Stroboscopic effect occurred in Fluroscent lamps.
22. Use of commutator in DC Machine is convert alternating current to Direct current.
23. I = 50 cos 1256t then frequency of the current is 200Hz
24. In a DC Machine No of poles is P, speed of the machine is N rpm then frequency of the developed voltage is f = PN / 120.
25. I is the current, C is the capacitance, V is the voltage then I / CV is equal to frequency.
26. Capacitor connected across the Mercury Vapour lamps for
I don’t know exactly but I put improve the PF.
27. Mho relay is used for Long transmission lines protection.
28. Transformer works on the principle of Mutual Induction principle.
29. Coefficient of coupling in inductive line is K = M / √ ( L1 L2 )
30. Surge impedance Z = √ (L / C ).
31. In a series R-C circuit applying DC then initial current is Zero.
32. Peak to Peak voltage if signal is 100 V. Then RMS value of that signal is 50 / √2.
33. 100 V full wave rectifier RMS value is 100 / √ 2.
34. In a transformer oil is used for both Insulation and Cooling. ( not for lubrication).
35. For reducing corona which type of conductor is used Circular.
36. Breather in transformer is used for absorb the moisture content in the air.
37. In a transformer core loss is 100 W, Copper loss is 400W, then maximum efficiency occurs at 1 / 2 load.
38. Main purpose of circuit breaker is Current interrupting.
39. To measure 10mv at 75Hz which instrument is used. I don’t know exact answer but answers are a) CRO b) VTVM.
40. In a power system PF improving capacitor is measured in KVAR.
41. In a power system capacitor is connecting in series with transmission line is to reduce the inductive effect of transformer.
42. FET is used as a Variable Capacitor.
43. In domestic wiring Lights and Fans are connected in Parallel.
44. Lead sheath is used for cable to ingress the moisture and gas.
45. Pin type insulators are not used beyond 33KV.
46. The angle between the Main field flux and Armature flux Is Torque angle.
47. In a synchronous machine at what angle the maximum power developed ?
I put the answer is 900
48. In a circuit current is 100 A. Power factor is 0.8. Then impedance is equal to 86.6 + j 50.
49. Die is used for making threads on conduits.
50. For a transformer, transmission ratio is 5. R = 0.1Ω. Then resistance referred to secondary is 2.5Ω.
51. Economizer purpose in Thermal power plants is To heat the feed water with flue gases.
52. when a shunt generator running at 1000rpm it develops 200V. If the speed increased to 1200rpm the induced EMF is 240 V.
53. Ferranti effect occurs when Transmission line is lightly loaded.
54. In nuclear reactor graphite is used for Moderator.
55. For a 1500 rpm machine frequency and poles reduced to half, then the value of the speed becomes 1500 rpm.
56. For efficient operation of the Voltage controlled Inverter – Load and Source inductances are small.
57. In transmission lines Arcing horns protect the Insulators.
58. for a synchronous machine Name plate details are 1000MW and 0.8 PF it means that it supplies 1000Mw when load is connected to constant 0.8 PF.
59. Fusing factor is equal to--- Minimum fusing current / current rating of element.
60. Flywheel is fitted for –
a) continuously varying load b) Inpact load C) Short time loads. I put the answer is Impact load.
61. When temperature increased the dielectric strength of the material is decreased.
62. In PLC, HSC stands for – I don’t know the answer I put the High Speed Counter.
63. In PLC, Double division instruction is ---I don’t know the answer I put DDV.
64. In a PLC, the MOD signal is used to—I don’t know the answer I Put Parallel communicator.
65. Tesla is the unit of Electric Flux Density.
66. Two 3-Ф, 50 Hz squirrel cage induction motors are there. Each motor have 36 slots. If 1 motor have 3 slots / phase / pole. Another have 2 slots / phase / pole. The ratio of speeds of 2 motors is----
Sol : in 1 st motor No of slots per pole is 3 X 3 = 9 slots
Then Total no of poles = 36 /9 = 4 poles
Then speed of the 1 st motor = 120 X 50 / 4 = 1500 rpm
in 2 nd motor No of slots per pole is 2 X 3 = 6 slots
Then Total no of poles = 36 /6 = 6 poles
Then speed of the 2 nd motor = 120 X 50 / 6 = 1000 rpm
Then ratio of the 2 motors = 1500 : 1000
= 3 : 2
67. One characterstic is given i.e Externa and internal characterstics of DC shunt generator.
68. One question belongs to protection for Bus bar protection – I put Differential protection
69. In digital system which adder is useful for add 2 binary numbers – Half adder.
70. A 3 phase induction motor is operating at slip s. If its two supply loads are interchanges, then its slip at that instant will be = 2-S
71. A wound rotor induction motor runs with a slip of 0.03 when developing full load torque. Its rotor resistance is 0.25 Ω per phase. If an external resistance of 0.5 Ω per phase is connected across slip rings. What is the slip for full load torque ? 0.09.
72. single phase midpoint cyclo converter stepdown output frequency is equal to – I don’t know the answer but I put fs / 4.
73. Bus bar protection – Differential protection.
74. CT connections for star to delta transformer. – Delta to star connection.
75. One question about Thevenin equivalent circuit of simple resistance circuit.
76. Which device is used for protection of thyristror from dv/dt- Snubber Ckt
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