electrical

Three Phase Induction Motor MCQ Questions and Answers Page - 6

1.

The 3-phase induction motor provided with open slots has

Answer/ Hint      

Answer : D

Explanation :

2.

Semi closed or totally closed slots are used in induction motors essentially to

Answer/ Hint      

Answer : D

Explanation :

3.

The stator of a small (up to 5hp) induction motor is provided with

Answer/ Hint      

Answer : C

Explanation :

4.

“Cogging” in induction motor occurs when

Answer/ Hint      

Answer : C

Explanation :

5.

In a 3-phase induction motor, the stator slots are

Answer/ Hint      

Answer : C

Explanation :

6.

In a 3-phase induction motor, the number of slots on stator is not kept an exact multiple of the number of rotor slots because it

Answer/ Hint      

Answer : B

Explanation :

7.

The difference between the number of stator slots and that of rotor slots in an induction motor should not be equal to P, 2P or 5P. It is essential in order to avoid

Answer/ Hint      

Answer : A

Explanation :

8.

The rotor slots in a 3-phase induction motor are kept inclined this phenomenon is known as

Answer/ Hint      

Answer : A

Explanation :

9.

In an induction motor, skewing of motor bars reduces

Answer/ Hint      

Answer : B

Explanation :

10.

Skew of rotor bar eliminates

Answer/ Hint      

Answer : A

Explanation :

11.

Jogging of an induction motor is

Answer/ Hint      

Answer : A

Explanation :

12.

In 3-phase induction motors, sometimes copper bars are placed deep in the rotor. It is done in order to improve

Answer/ Hint      

Answer : B

Explanation :

13.

In a squirrel cage induction motor high starting torque is achieved by using

Answer/ Hint      

Answer : C

Explanation :

14.

The outer cage of a double squirrel rotor consists of

Answer/ Hint      

Answer : A

Explanation :

15.

In double cage induction motor the inner cage has

Answer/ Hint      

Answer : C

Explanation :

16.

In the equivalent circuit of a double cage induction motor, the two rotor cages can be considered

Answer/ Hint      

Answer : A

Explanation :

17.

The advantage of the double squirrel cage induction motor over single cage rotor is that its

Answer/ Hint      

Answer : D

Explanation :

18.

In a double squirrel cage induction motor, the resistance of upper cage is ____that of inner cage.

Answer/ Hint      

Answer : B

Explanation :

19.

The deep bar rotors of double cage rotors are employed to

Answer/ Hint      

Answer : A

Explanation :

20.

For high starting torque, the most suitable 3-phsae induction motor is ___induction motor

Answer/ Hint      

Answer : A

Explanation :

21.

Which of the following ac motor is widely used?

Answer/ Hint      

Answer : A

Explanation :

22.

A squirrel cage induction motor is not favored when ______ in the main consideration

Answer/ Hint      

Answer : C

Explanation :

23.

A slip ring induction motor is recommended for application requiring

Answer/ Hint      

Answer : D

Explanation :

24.

Unbalanced 3-phase voltage supply to an induction motor causes excessive heating of

Answer/ Hint      

Answer : A

Explanation :

25.

Unbalance supply voltage given to a 3- phase delta connected induction motor will cause

Answer/ Hint      

Answer : C

Explanation :

26.

Single phase preventer

Answer/ Hint      

Answer : C

Explanation :

27.

If one of the 3-phase of supply to an induction motor fails, may be due to any reason, when the motor is running normally, the motor will

Answer/ Hint      

Answer : D

Explanation :

28.

Increase in supply voltage to a 3-phase induction motor will not cause

Answer/ Hint      

Answer : C

Explanation :

29.

Decrease in supply voltage to a 3-phase induction motor will not cause

Answer/ Hint      

Answer : B

Explanation :

30.

If a 3-phase 350 V, 50Hz, 1440 rpm induction motor is operated on 420V, 60Hz supply, then the torque will

Answer/ Hint      

Answer : C

Explanation :

31.

With the increase in supply frequency ___decreases (s)

Answer/ Hint      

Answer : D

Explanation :

32.

This size of a high-speed motor is ____in comparison to that of a low speed motor for the same kW output

Answer/ Hint      

Answer : A

Explanation :

33.

Which of the following induction motors will operate on the lowest value of power factor?

Answer/ Hint      

Answer : A

Explanation :

34.

For starting a 3-phase induction motor ____winding is to be connected to 3 phase ac supply

Answer/ Hint      

Answer : B

Explanation :

35.

The starting current of a 3-phase induction motor is about of its full load rated current

Answer/ Hint      

Answer : C

Explanation :

36.

The purpose of the starter is to

Answer/ Hint      

Answer : A

Explanation :

37.

Direct on line starter can be used for small capacity ____induction motors.

Answer/ Hint      

Answer : C

Explanation :

38.

For starting a small induction motor DOL starter is used in place or iron clad triple pole (ICTP) switch as it

Answer/ Hint      

Answer : A

Explanation :

39.

Whenever any polyphase induction motor is loaded

Answer/ Hint      

Answer : D

Explanation :

40.

A 3-phase induction motor is running at a load of the rated torque. What happens when one of the outer mains is interrupted while the motor is running?

Answer/ Hint      

Answer : B

Explanation :

41.

What is the function of putting resistance in parallel to one phase of 3-phase induction motor?

Answer/ Hint      

Answer : B

Explanation :

42.

What is the disadvantage of the speed control of slip-ring induction motor with the help of resistances in the rotor circuit?

Answer/ Hint      

Answer : B

Explanation :

43.

The reactance per phase as compared to the resistance per phase of an induction motor is

Answer/ Hint      

Answer : B

Explanation :

44.

What is the disadvantage of starting an induction motor with star-delta starter?

Answer/ Hint      

Answer : A

Explanation :

45.

An induction motor has a rated speed of 720 r.p.m. how many poles has it rotating magnetic field?

Answer/ Hint      

Answer : A

Explanation :

46.

Which of the following methods of speed control is not affected through the stator side?

Answer/ Hint      

Answer : B

Explanation :

47.

During starting of an induction motor hums, the probable cause could be

Answer/ Hint      

Answer : D

Explanation :

48.

The possible number of different speeds that can be obtained by connecting two motors in cascade is

Answer/ Hint      

Answer : B

Explanation :

49.

The induction motor which is provided with open slots have

Answer/ Hint      

Answer : A

Explanation :

50.

For a 50 H.P motor, which type of rotor will be preferred?

Answer/ Hint      

Answer : B

Explanation :

51.

If a three-phase squirrel cage induction motor run slow, which of the following could not be the reason for the same?

Answer/ Hint      

Answer : D

Explanation :

52.

The probable reason for an induction motor running too hot could be

Answer/ Hint      

Answer : D

Explanation :

53.

Which of the following motors has the highest power to weight ratio?

Answer/ Hint      

Answer : D

Explanation :

54.

In a 3-phase induction motor, iron loss

Answer/ Hint      

Answer : A

Explanation :

55.

Which of the following parameters for an induction motor varies as square of the supply voltage?

Answer/ Hint      

Answer : D

Explanation :

56.

Is an induction motor is to be run on unbalanced supply, then it should be run at

Answer/ Hint      

Answer : A

Explanation :

57.

In case single phasing occurs in delta connected motor

Answer/ Hint      

Answer : A

Explanation :

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