electrical

Transformer MCQ Objective Questions and Answers Page - 5

1.

Transformer will operate at maximum efficiency when

Answer/ Hint      

Answer : C

Explanation :

2.

Power transformers are designed to have maximum efficiency around _____full load.

Answer/ Hint      

Answer : A

Explanation :

3.

The transformer efficiency will be maximum at a power factor of

Answer/ Hint      

Answer : B

Explanation :

4.

If P1 and P2 be the iron and copper losses of a transformer at full load and the maximum efficiency is at 75 % of the full load, then what is the ratio of P1 and P2?

Answer/ Hint      

Answer : A

Explanation :

5.

What is load at which maximum efficiency occurs in case of a 100 kVA transformer with iron loss of 1 kW and full load copper loss of 2 kW?

Answer/ Hint      

Answer : B

Explanation :

6.

A 500 kVA transformer has constant loss of 500 W and copper losses at full load are 2,000W. Then at what load, is the efficiency maximum?

Answer/ Hint      

Answer : A

Explanation :

7.

A 2 kVA transformer has iron loss of 150 W and full load coper loss of 250 W. The maximum efficiency of the transformer would occur when the total loss is

Answer/ Hint      

Answer : C

Explanation :

8.

A single-phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is

Answer/ Hint      

Answer : D

Explanation :

9.

The all-day efficiency of a distribution transformer will be high with low

Answer/ Hint      

Answer : D

Explanation :

10.

The all-day efficiency of a transformer depends primarily on

Answer/ Hint      

Answer : D

Explanation :

11.

A single-phase transformer is to be switched to the supply to have minimum inrush current. The switch should be closed at

Answer/ Hint      

Answer : A

Explanation :

12.

The desirable properties of transformer core material are

Answer/ Hint      

Answer : C

Explanation :

13.

The use of higher flux density in the transformer design

Answer/ Hint      

Answer : A

Explanation :

14.

What does the use of higher flux density value in a transformer design lead to

Answer/ Hint      

Answer : B

Explanation :

15.

The size of the transformer core depends upon

Answer/ Hint      

Answer : D

Explanation :

16.

Ferrite cores are employed in high frequency transformers due to their

Answer/ Hint      

Answer : B

Explanation :

17.

What is the core loss in a high frequency ferrite core transformer used in SMPS power supply?

Answer/ Hint      

Answer : D

Explanation :

18.

The changes in volume of transformer cooling oil due to variations of atmospheric temperature during day and night is taken care of by which part of transformer?

Answer/ Hint      

Answer : A

Explanation :

19.

An ideal transformer is one which has

Answer/ Hint      

Answer : A

Explanation :

20.

When a given transformer is run at its rated voltage but reduced frequency, its

Answer/ Hint      

Answer : D

Explanation :

21.

In an actual transformer the iron loss remains practically constant from no-load to full-load because

Answer/ Hint      

Answer : C

Explanation :

22.

An ideal transformer will have maximum efficiency at load such that

Answer/ Hint      

Answer : A

Explanation :

23.

If the supply frequency to the transformer is increased, the iron loss will

Answer/ Hint      

Answer : C

Explanation :

24.

Negative voltage regulation is indicative that the load is

Answer/ Hint      

Answer : A

Explanation :

25.

Iron loss of a transformer can be measured by

Answer/ Hint      

Answer : A

Explanation :

26.

When secondary of a current transformer is open-circuited its iron core will be

Answer/ Hint      

Answer : A

Explanation :

27.

The transformer laminations are insulated from each other by

Answer/ Hint      

Answer : B

Explanation :

28.

Which type of winding is used in 3-phase shell-type transformer?

Answer/ Hint      

Answer : B

Explanation :

29.

During open circuit test of a transformer

Answer/ Hint      

Answer : A

Explanation :

30.

Open circuit test on transformers is conducted to determine

Answer/ Hint      

Answer : C

Explanation :

31.

Short circuit test on transformers is conducted to determine

Answer/ Hint      

Answer : B

Explanation :

32.

For the parallel operation of single-phase transformers, it is necessary that they should have

Answer/ Hint      

Answer : B

Explanation :

33.

The transformer oil should have ………. volatility and ………. Viscosity

Answer/ Hint      

Answer : A

Explanation :

34.

The function of breather in a transformer is

Answer/ Hint      

Answer : D

Explanation :

35.

The secondary winding of which of the following transformers is always kept close

Answer/ Hint      

Answer : D

Explanation :

36.

The size of transformer core will depend on

Answer/ Hint      

Answer : D

Explanation :

37.

Natural air cooling is generally restricted for transformers up to

Answer/ Hint      

Answer : A

Explanation :

38.

The core and windings of a transformer are put in a steel tank in order to

Answer/ Hint      

Answer : B

Explanation :

39.

conservator (for transformer) is used

Answer/ Hint      

Answer : A

Explanation :

40.

In a large power transformer, a conservator drum is provided above the completely oil filled transformer tank and connected to it by a a short pipe. The conservator drum is linked to external air through a breather. What is the purpose of providing the conservator?

Answer/ Hint      

Answer : C

Explanation :

41.

Sludge formation in transformer oil is due to which one of the following?

Answer/ Hint      

Answer : D

Explanation :

42.

In a power transformer, the breather is provided in order to

Answer/ Hint      

Answer : B

Explanation :

43.

The chemical used in breather of a transformer should have quality of

Answer/ Hint      

Answer : A

Explanation :

44.

Malfunctioning of the Buchholz relay may be caused due to

Answer/ Hint      

Answer : C

Explanation :

45.

Which of the following statements associated with Buchholz relay is not TRUE?

Answer/ Hint      

Answer : C

Explanation :

46.

A Buchholz relay is used for

Answer/ Hint      

Answer : A

Explanation :

47.

If a transformer is switched on to a voltage more than the rated voltage

Answer/ Hint      

Answer : A

Explanation :

48.

Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is

Answer/ Hint      

Answer : A

Explanation :

49.

Minimum voltage regulation occurs when the power factor of the load is

Answer/ Hint      

Answer : C

Explanation :

50.

In a step-down transformer, there is a change of 15 A in the load current, this result in change of supply current of

Answer/ Hint      

Answer : A

Explanation :

51.

The efficiency of transformers compared with that of electric motors of the same power are

Answer/ Hint      

Answer : C

Explanation :

52.

The short-circuit voltage of a transformer mainly depends upon the

Answer/ Hint      

Answer : A

Explanation :

53.

In a transformer, electric power is transferred from one coil to the other coil in a transformer

Answer/ Hint      

Answer : B

Explanation :

54.

In an ideal transformer, on no-load, the primary voltage is balanced by

Answer/ Hint      

Answer : B

Explanation :

55.

As per name plates of a transformer, the secondary normal voltage is 220 Which of the following statement is correct

Answer/ Hint      

Answer : B

Explanation :

56.

A transformer is working at its maximum efficiency. Its iron loss is 1 KW. Its copper loss will be

Answer/ Hint      

Answer : D

Explanation :

<< Previous
Transformer MCQ Objective Questions and Answers Page - 5