Transformer MCQ

In this page, you can solve transformer MCQ or multiple-choice questions. You can also analyse your answers at the same time by clicking Answer tab.

1. While performing the short-circuit test on the transformer the _________ side is short-circuited.

  1. High voltage side
  2. Low voltage side
  3. Primary side
  4. Secondary side

Answer
Answer. b

2. Which of the following is not a part of the transformer installation?

  1. Conservator
  2. Breather
  3. Buchholz relay
  4. Exciter

Answer
Answer. d

3. The purpose of providing an iron core in a transformer is to

  1. provide support to windings
  2. reduce hysteresis loss
  3. decrease the reluctance of the magnetic path
  4. reduce eddy current losses

Answer
Answer. c

4. The no-load current in a transformer

  1. lags behind the voltage by about 75°
  2. leads the voltage by about 75°
  3. lags behind the voltage by about 15°
  4. leads the voltage by about 15°

Answer
Answer. a

5. The efficiency of a transformer will be maximum when

  1. copper losses = iron losses
  2. copper losses = hysteresis losses
  3. eddy current losses = copper losses
  4. hysteresis losses = eddy current losses

Answer
Answer. a

6. The permissible flux density in the case of cold-rolled grain-oriented steel is around

  1. 3.2 Wb/m2
  2. 1.7 Wb/m2
  3. 3.7 Wb/m2
  4. 5.7 Wb/m2

Answer
Answer. b

7. Sumpner’s test is conducted on transformers to determine

  1. temperature
  2. stray losses
  3. all-day efficiency
  4. none of the above

Answer
Answer. a

8. The dielectric strength of transformer oil is expected to be

  1. 1 kV
  2. 33 kV
  3. 100 kV
  4. 330 kV

Answer
Answer. b

9. No-load test on a transformer is carried out to determine

  1. copper loss
  2. magnetising current
  3. magnetising current and loss
  4. the efficiency of the transformer

Answer
Answer. c

10. The path of magnetic flux in a transformer should have

  1. high resistance
  2. high reluctance
  3. low resistance
  4. low reluctance

Answer
Answer. d

11. The no-load current drawn by the transformer is usually what per cent of the full-load current?

  1. 2 to 5 %
  2. 0.2 to 0.5 %
  3. 20 to 30 %
  4. 12 to 15 %

Answer
Answer. a

12. The degree of mechanical vibrations produced by the laminations of a transformer depends on

  1. tightness of clamping
  2. gauge of laminations
  3. size of laminations
  4. all of the above

Answer
Answer. d

13. A transformer core is laminated to

  1. reduce hysteresis loss
  2. reduce eddy current losses
  3. reduce copper losses
  4. reduce all above losses

Answer
Answer. b

14. In a transformer, the energy is conveyed from primary to secondary

  1. through cooling coil
  2. through air
  3. by the flux
  4. none of the above

Answer
Answer. c

15. Which of the following does not change in a transformer?

  1. Frequency
  2. Voltage
  3. Current
  4. All of the above

Answer
Answer. a

16. The no-load primary input is approximately equal to the

  1. Iron loss of a transformer
  2. Sum of Iron loss and copper loss of a transformer
  3. Neither Iron loss of transformer nor copper loss
  4. Copper loss of a transformer

Answer
Answer. a

17. While conducting short-circuit test on a transformer the following side is short-circuited

  1. Primary side
  2. HV side
  3. LV side
  4. None of these

Answer
Answer. c

18. The ordinary efficiency of a transformer is maximum when

  1. it runs at full-load
  2. it runs at half full-load
  3. its copper loss equals iron loss
  4. it runs overload

Answer
Answer. c

19. When a 400-Hz transformer is operated at 50 Hz, its kVA rating is

  1. reduced to 1/8
  2. increased 8 times
  3. unaffected
  4. determined by load on secondary

Answer
Answer. a

20. During the short-circuit test, the iron loss of a transformer is negligible because

  1. the entire input is just sufficient to meet copper losses only
  2. voltage applied across the HV (High Voltage) side is a small fraction of the rated voltage and so its flux
  3. iron core becomes fully saturated
  4. supply frequency is held constant

Answer
Answer. b

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