electrical

Transformer MCQ Objective Questions and Answers Page - 2

1.

A single phase transformer rated for 220/240V,  50Hz operates at no load at 220 V , 40 Hz. This frequency operation at rated voltage  results in which one of the following

Answer/ Hint      

Answer : D

Explanation :

2.

A 50 Hz transformer having equal hysteresis and eddy current losses at rated excitation is operated at 45Hz at 90% of its rated voltage . Compared to rated operating point, the core loses under thi

Answer/ Hint      

Answer : C

Explanation :

3.

A single phase transformer when supplied form 220V , 50 Hz has eddy current loss of 50W. If the transformer is connected to a voltage of 330V, 50Hz the eddy current loss will be

Answer/ Hint      

Answer : B

Explanation :

4.

1 kVA, 230V, 50Hz single phase transformer has an eddy  current loss of 30 watts. The eddy current loss when the transformer is excited by a dc source of same voltage will be

Answer/ Hint      

Answer : D

Explanation :

5.

At 50 Hz operation, a single phase transformer has hysteresis loss of  200 W and eddy current loss of 100 W. Its core loss at 60 Hz operation will be

Answer/ Hint      

Answer : C

Explanation :

6.

Can a 50Hz transformer be used for 25Hz, if the input voltage is maintained constant at the rated value corresponding to 50H

Answer/ Hint      

Answer : B

Explanation :

7.

On no load phasor diagram of transformer, the core loss component of the current remains in phase with

Answer/ Hint      

Answer : B

Explanation :

8.

In a transformer core, third and fifth harmonic components of fluxes are respectively 10% and 4% of the fundamental flux. The third and fith harmonic induced emfs in the winding in terms of the fun

Answer/ Hint      

Answer : A

Explanation :

9.

If a sinusoidal voltage source is connected to a power transformer, its no load current would be

Answer/ Hint      

Answer : D

Explanation :

10.

In a transformer , the exciting current will be in phase quadrature with the impressed voltage provided

Answer/ Hint      

Answer : C

Explanation :

11.

The power factor of a power transformer on no load will bne about

Answer/ Hint      

Answer : D

Explanation :

12.

The power factor of a transformer on no loadis poor due to

Answer/ Hint      

Answer : A

Explanation :

13.

If in a transformer core a material having high reluctance path but having same hystersis loop is employed

Answer/ Hint      

Answer : B

Explanation :

14.

Primary winding of a transformer comprises of two identical windings in parallel. If one winding is removed, magnetizing current will b

Answer/ Hint      

Answer : C

Explanation :

15.

The core flux of a practical transformer  with a resistance load

Answer/ Hint      

Answer : A

Explanation :

16.

The inductive reactance of a transformer depends on

Answer/ Hint      

Answer : D

Explanation :

17.

The flux in transformer core

Answer/ Hint      

Answer : C

Explanation :

18.

The mutual flux in a loaded transformer can be varied by varying

Answer/ Hint      

Answer : D

Explanation :

19.

The primary ampere turns are counter balanced by

Answer/ Hint      

Answer : A

Explanation :

20.

In a transformer_____ decreases with the increase in leakage flux

Answer/ Hint      

Answer : C

Explanation :

21.

In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are

Answer/ Hint      

Answer : C

Explanation :

22.

A common method of cooling a power transformer is

Answer/ Hint      

Answer : C

Explanation :

23.

The no-load current in a transformer lags behind the applied voltage by an angle of about

Answer/ Hint      

Answer : D

Explanation :

24.

In a transformer routine efficiency depends upon

Answer/ Hint      

Answer : D

Explanation :

25.

In the transformer the function of a conservator is to

Answer/ Hint      

Answer : C

Explanation :

26.

Natural oil cooling is used for transformer upto a rating of

Answer/ Hint      

Answer : A

Explanation :

27.

Power transformers are designed to have maximum efficiency at

Answer/ Hint      

Answer : A

Explanation :

28.

The maximum efficiency of a distribution transformer is

Answer/ Hint      

Answer : B

Explanation :

29.

Transformer breathes in when

Answer/ Hint      

Answer : B

Explanation :

30.

No-load current of a transformer has

Answer/ Hint      

Answer : D

Explanation :

31.

Spacer are provided between adjacent coils

Answer/ Hint      

Answer : A

Explanation :

32.

Greater the secondary leakage flux

Answer/ Hint      

Answer : A

Explanation :

33.

The purpose of providing iron core in a step-up transformer is

Answer/ Hint      

Answer : C

Explanation :

34.

The power transformer is a constant

Answer/ Hint      

Answer : D

Explanation :

35.

Two transformers operating in parallel will share the load depending upon their

Answer/ Hint      

Answer : B

Explanation :

36.

What will happen if the transformers working in parallel are not connected with regard to polarity?

Answer/ Hint      

Answer : B

Explanation :

37.

If the percentage impedances of the two transformers working in parallel is different, then

Answer/ Hint      

Answer : D

Explanation :

38.

In a transformer the tapings are generally provided on

Answer/ Hint      

Answer : C

Explanation :

39.

Cores of large power transformers are made from which one of the followings?

Answer/ Hint      

Answer : C

Explanation :

40.

Grain oriented laminated sheet steel in transformer reduces

Answer/ Hint      

Answer : C

Explanation :

41.

Silicon content in iron laminations is kept within 5% as it

Answer/ Hint      

Answer : C

Explanation :

42.

The permissible flux density in cold rolled grain-oriented steel is about

Answer/ Hint      

Answer : A

Explanation :

43.

If the iron core of a transformer is replaced by an air core, then the hysteresis losses in the transformer will

Answer/ Hint      

Answer : D

Explanation :

44.

Which of the following will improve the mutual coupling between primary and secondary circuits?

Answer/ Hint      

Answer : D

Explanation :

45.

In order to reduce the hysteresis loss

Answer/ Hint      

Answer : B

Explanation :

46.

Why is the core of the transformer built up of laminations?

Answer/ Hint      

Answer : A

Explanation :

47.

When are eddy current losses in a transformer reduced?

Answer/ Hint      

Answer : D

Explanation :

48.

Transformer core laminations are coated with an enamel layer in order to

Answer/ Hint      

Answer : C

Explanation :

49.

A shell-type transformer has

Answer/ Hint      

Answer : B

Explanation :

50.

A transformer can have regulation closer to zero

Answer/ Hint      

Answer : C

Explanation :

51.

A transformer transforms

Answer/ Hint      

Answer : D

Explanation :

52.

Which of the following is not the standard voltage for power supply in India?

Answer/ Hint      

Answer : D

Explanation :

53.

Reduction in core losses and increase in permeability are obtained with transformer employing

Answer/ Hint      

Answer : A

Explanation :

54.

In a power or distribution transformer about 10% end turns are heavily insulated

Answer/ Hint      

Answer : A

Explanation :

55.

For a given applied voltage, with the increase in frequency of the applied voltage

Answer/ Hint      

Answer : C

Explanation :

56.

Losses which occurs in rotating electric machines and do not occurs in transformers are

Answer/ Hint      

Answer : A

Explanation :

57.

In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are

Answer/ Hint      

Answer : A

Explanation :

58.

Which of the following statements regarding an ideal single-phase transformer having a turn ratio of 1:2 and drawing a current of 10 A from 200V A.C supply is incorrect?

Answer/ Hint      

Answer : D

Explanation :

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