electrical

Transformer MCQ Objective Questions and Answers Page - 4

1.

The full load copper loss and iron loss of a transformer are 6,400 W and 5,000 W respectively. The copper loss and iron loss at half load will be respectively

Answer/ Hint      

Answer : D

Explanation :

2.

If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

Answer/ Hint      

Answer : D

Explanation :

3.

The total iron loss in a transformer core at normal flux density was measured at 25 Hz and at 50 Hz and was found to be 250W and 800 W respectively. The hysteresis loss at 50Hz would be

Answer/ Hint      

Answer : C

Explanation :

4.

The hysteresis and eddy current loss of 1-phase transformer working on 200 V, 50Hz supply and Ph and Pe respectively. The percentage decrease in these losses when operated on 160 V , 40Hz supply would respectively be

Answer/ Hint      

Answer : B

Explanation :

5.

The main purpose of performing open circuit on a transformer is to measure its

Answer/ Hint      

Answer : B

Explanation :

6.

Open circuit test in a transformer is performed with

Answer/ Hint      

Answer : A

Explanation :

7.

The open circuit test on a transformer is usually performed by exciting the low voltage winding. This is because

Answer/ Hint      

Answer : A

Explanation :

8.

The open circuit test on a transformer gives

Answer/ Hint      

Answer : B

Explanation :

9.

In transformers, which of the following statements is valid?

Answer/ Hint      

Answer : D

Explanation :

10.

During short circuit test, the core losses are negligible. This is because

Answer/ Hint      

Answer : A

Explanation :

11.

While performing the open circuit and short circuit tests on a transformer to determine parameters the status of the low voltage (LV) and high voltage (HV) windings will be such that

Answer/ Hint      

Answer : B

Explanation :

12.

For a transformer to be tested at full load conditions but consuming only losses form the mains, we do

Answer/ Hint      

Answer : C

Explanation :

13.

The efficiency of two identical transformers under load conditions can be determined by

Answer/ Hint      

Answer : A

Explanation :

14.

The efficiency of a power transformer can be determined indirectly by

Answer/ Hint      

Answer : C

Explanation :

15.

The transformer efficiency at relatively light loads is quite low. This is due to

Answer/ Hint      

Answer : C

Explanation :

16.

The transformer efficiency, under heavy loads is comparatively low doe to

Answer/ Hint      

Answer : A

Explanation :

17.

The full load copper loss and iron loss of a transformer are 6,400 W and 500 W, respectively. The above copper loss and iron loss at half load will be

Answer/ Hint      

Answer : D

Explanation :

18.

The efficiency of a 100 kVA transformer is 0.98 at full as well as half load. For this transformer at full load the copper loss

Answer/ Hint      

Answer : C

Explanation :

19.

Buchholz’s relay gives warning and protection against

Answer/ Hint      

Answer : A

Explanation :

20.

The magnetizing current of a transformer is usually small because it has

Answer/ Hint      

Answer : A

Explanation :

21.

Which of the following does not change in an ordinary transformer?

Answer/ Hint      

Answer : A

Explanation :

22.

Which of the following properties is not necessarily desirable for the material for transformer core?

Answer/ Hint      

Answer : C

Explanation :

23.

The leakage flux in a transformer depends upon

Answer/ Hint      

Answer : A

Explanation :

24.

The path of magnetic flux in transformer should have

Answer/ Hint      

Answer : B

Explanation :

25.

Noise level test in a transformer is a

Answer/ Hint      

Answer : C

Explanation :

26.

Which of the following is not a routine test on transformers?

Answer/ Hint      

Answer : C

Explanation :

27.

A transformer can have zero voltage regulation at

Answer/ Hint      

Answer : A

Explanation :

28.

Helical coils can be used on

Answer/ Hint      

Answer : A

Explanation :

29.

Harmonics in transformer result in

Answer/ Hint      

Answer : D

Explanation :

30.

The core used in high frequency transformer is usually

Answer/ Hint      

Answer : C

Explanation :

31.

The full-load copper loss of a transformer is 1600 W.at the full-load, the copper loss will be

Answer/ Hint      

Answer : D

Explanation :

32.

The value of flux involved in the e.m.f equation of a transformer is

Answer/ Hint      

Answer : C

Explanation :

33.

Silicon steel used in lamination mainly reduce

Answer/ Hint      

Answer : A

Explanation :

34.

Which winding of the transformer has less cross-sectional area?

Answer/ Hint      

Answer : D

Explanation :

35.

Power transformers are generally designed to have maximum efficiency around?

Answer/ Hint      

Answer : C

Explanation :

36.

Which of the following is the main advantage of an auto-transformer over a two-winding transformer?

Answer/ Hint      

Answer : B

Explanation :

37.

During short-circuit test iron losses are negligible because

Answer/ Hint      

Answer : C

Explanation :

38.

The transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in

Answer/ Hint      

Answer : D

Explanation :

39.

In a large capacity transformer, 5% of the turns at the end of hv winding are provided with extra insulation so as to provide protection.

Answer/ Hint      

Answer : C

Explanation :

40.

When a transformer winding suffers a short circuit, the adjoining turns of the same winding experience

Answer/ Hint      

Answer : A

Explanation :

41.

Under short circuit condition, the windings of transformer having 5% impedance will experience a radial force

Answer/ Hint      

Answer : D

Explanation :

42.

Major insulation in a transformer is the insulation between the

Answer/ Hint      

Answer : D

Explanation :

43.

Minor insulation in a transformer is the insulation between the

Answer/ Hint      

Answer : D

Explanation :

44.

In a transformer an insulating material may fail due to

Answer/ Hint      

Answer : D

Explanation :

45.

The function of oil in a transformer is

Answer/ Hint      

Answer : A

Explanation :

46.

The color of fresh dielectric oil used in transformers is

Answer/ Hint      

Answer : B

Explanation :

47.

The transformer oil should have

Answer/ Hint      

Answer : D

Explanation :

48.

Transformer oil must be free from

Answer/ Hint      

Answer : A

Explanation :

49.

Which of the following loss in a transformer is zero even at full load?

Answer/ Hint      

Answer : B

Explanation :

50.

Which of the following is the most likely source of harmonic in transformer?

Answer/ Hint      

Answer : D

Explanation :

51.

If a transformer is continuously operated the maximum temperature rise will occur

Answer/ Hint      

Answer : B

Explanation :

52.

The hum in a transformer is mainly attributed to

Answer/ Hint      

Answer : C

Explanation :

53.

The maximum load that power transformer can carry is limited by its

Answer/ Hint      

Answer : C

Explanation :

54.

The efficiency of a transformer, under heavy loads, is comparatively low because

Answer/ Hint      

Answer : A

Explanation :

55.

An open-circuit test on a transformer is conducted primarily to measure

Answer/ Hint      

Answer : C

Explanation :

56.

A no-load test is performed on a transformer to determine

Answer/ Hint      

Answer : D

Explanation :

57.

The voltage transformation ratio of a transformer is equal to the ratio of

Answer/ Hint      

Answer : C

Explanation :

58.

Part of the transformer which is most subject to damage from overheating is

Answer/ Hint      

Answer : C

Explanation :

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