NHPC Paper

               NHPC Electrical Engineering Placement Paper for Trainee Engineer

1. For interrupting capacitive currents which Circuit Breaker (CB) is used
a) SF6 CB
b) Oil CB
c) Vacuum CB
d) Air blast CB
Ans: Vacuum CB

2. For V/F control, when frequency is increased in transformer
a) Core loss component current increases, Magnetizing component current decreases
b) Core loss component current increases, Magnetizing component current increases
c) Core loss component current decreases, Magnetizing component current decreases
d) Core loss component current decreases, Magnetizing component current increases
Ans: Core loss component current decreases, Magnetizing component current decreases

3. In ceiling fan the angle between auxiliary winding a main winding is
a) 0 deg
b) 90 deg
c) 180 deg
d) 360 deg
Ans: 90 deg

4. In a shaded pole motor, shaded rings are used to
Ans: Field flux production

5. Practical method of improving string efficiency
a) Increasing crass arms length
b) Using different size of insulators
c) Using different insulator materials
d) Using of guard rings
Ans: Increasing crass arms length*

6. In which type of fault all 3-phase components are equal
a) L-G
b) L-L
c) L-L-G
d) 3-Phase fault
Ans: 3-Phase fault

7. 11/220 KV 100 MVA transformers, the primary base voltage rating is 10 KV then secondary base KV is
a) 10 KV
b) 220 KV
c) 220/sqrt3
Ans: 220/sqrt3

8. Water hamming effect is occurs in
a) Surge tank
b) Penstock
c) Turbine
d) Reservoir
Ans: Penstock

9. Transient stability can be improved by
a) By putting series capacitor
b) By using dynamic resister
c) Auto re-closers
d) All of the above
Ans: All of the above

10. If sending end voltage is Vs at no-load in a transmission line then receiving end voltage is if ABCD parameters of line is given
a) Vs
b) Vs/A
c) 0
d) Infinity
Ans: Vs/A

11. Harmonics are eliminated by using
a) Skewing of rotor
b) Distribution winding
c) Short pitch winding
d) All of the above
Ans: All of the above

12. For parallel operation of transformer at no load, then load shared are equal when
Ans: Impedance is proportional with respect to own KVA rating

13. In Induction motor Slip frequency of rotor current, when rotor speed is Nr. Then rotor producing slip field rotates with respect to stator is
a) Slip frequency
b) Nr
c) Ns
d) None
Ans: Ns

14. Good regulation means
Ans: Less fluctuation from no-load to full-load

15. At dead short circuit at terminals of Alternator then the current I is
a) ZPF Lag
b) ZPF lead
c) Unity power factor
d) 0.8 Power factor lag
Ans: ZPF Lag

16. Full scale Ammeter reading is 10 mA, Voltage across Ammeter is 100 mV. Then for 100 A measurements the power loss in the circuit is
a) 1 W
b) 10 W
c) 100 W
d) 1000 W
Ans: 10 W

17. When Alternator excitation increases and machine is operating at lagging power factor then
a) I increase
b) I decreases
c) No effect on current
d) None
Ans: I increase

18. Flue gases coming out from furnace is first going through
a) Turbine
b) Economizer
c) Air pre-heater
d) Chimney
Ans: Economizer

19. Two alternators rated are 200 KW at 4% regulation, 400 KW 5% regulation operating in parallel at 50HZ , when supply 600 KW the new frequency is
a) 50
b) 49
c) 51.3
d) 47.7
Ans: 47.7

20. Va and Vb are negative sequence component voltages the difference angle between Va and Vb with respect to Va is
a) 240
b) 120
c) 180
d) 360
Ans: 120

21. 4-Quadrent operation of chopper I is positive but V is may be positive are negative operates in which quadrant
a) 1 and 2
b) 2 and 3
c) 1 and 3
d) 1 and 4
Ans: 1 and 4

22. Heat convection, radiation, and conduction all are takes place in
a) Ice
b) Boiler
c) Refrigerator
d) Flue gases in pipe

23. When moving iron meter is used to measure d.c current what is the disadvantage

24. When maximum power transfer to load is
a) 20 W
b) 50 W
c) 100W
d) 0W
Ans: 0W

25. Current in 5 ohm resister is
a) 10 A
b) -10 A
c) 5 A
d) -5 A
Ans: -10 A