Transformer Multiple Choice Questions Answers In English - 02

1. No-load on a transformer is carried out to determine
(A) copper loss
(B) magnetizing current
(C) magnetizing current and loss
(D) efficiency of the transformer
Ans: C

2. Sumpner’s test is conducted on transformers to determine
(A) temperature
(B) stray losses
(C) all-day efficiency
(D) none of the above
Ans: A

3. The path of a magnetic flux in a transformer should have
(A) high resistance
(B) high reluctance
(C) low resistance
(D) low reluctance
Ans: D

4. The dielectric strength of transformer oil is expected to be
(A) lkV
(B) 33 kV
(C) 100 kV
(D) 330 kV
Ans: B

5. The permissible flux density in case of cold rolled grain oriented steel is around
(A) 1.7 Wb/m2
(B) 2.7 Wb/m2
(C) 3.7 Wb/m2
(D) 4.7 Wb/m2
Ans: A

6. Material used for construction of transformer core is usually
(A) wood
(B) copper
(C) aluminium
(D) silicon steel
Ans: D

7. No-load current in a transformer
(A) lags behind the voltage by about 75°
(B) leads the voltage by about 75°
(C) lags behind the voltage by about 15°
(D) leads the voltage by about 15°
Ans: A

8. The efficiency of a transformer will be maximum when
(A) copper losses = hysteresis losses
(B) hysteresis losses = eddy current losses
(C) eddy current losses = copper losses
(D) copper losses = iron losses
Ans: D

9. Which winding in a transformer has more number of turns ?
(A) Low voltage winding
(B) High voltage winding
(C) Primary winding
(D) Secondary winding
Ans: B

10. Primary winding of a transformer
(A) is always a low voltage winding
(B) is always a high voltage winding
(C) could either be a low voltage or high voltage winding
(D) none of the above
Ans: C

11. Efficiency of a power transformer is of the order of
(A) 100 per cent
(B) 98 per cent
(C) 50 per cent
(D) 25 per cent
Ans: B

12. A common method of cooling a power transformer is
(A) natural air cooling
(B) air blast cooling
(C) oil cooling
(D) any of the above
Ans: C

13. The no load current in a transformer lags behind the applied voltage by an angle of about
(A) 180°
(B) 120″
(C) 90°
(D) 75°
Ans: D

14. In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are
(A) friction and windage losses
(B) copper losses
(C) hysteresis and eddy current losses
(D) none of the above
Ans: C

15. If the percentage impedances of the two transformers working in parallel are different, then
(A) transformers will be overheated
(B) power factors of both the transformers will be same
(C) parallel operation will be not possible
(D) parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load
Ans: D

16. If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be
(A) R2/VK
(B) R2IK2
(C) R22!K2
(D) R22/K
Ans: B

17. In a transformer the tappings are generally provided on
(A) primary side
(B) secondary side
(C) low voltage side
(D) high voltage side
Ans: C

18. The transformer ratings are usually expressed in terms of
(A) volts
(B) amperes
(C) kW
(D) kVA
Ans: D

19. Transformer breaths in when
(A) load on it increases
(B) load on it decreases
(C) load remains constant
(D) none of the above
Ans: B

20. No-load current of a transformer has
(A) has high magnitude and low power factor
(B) has high magnitude and high power factor
(C) has small magnitude and high power factor
(D) has small magnitude and low power factor
Ans: D