electrical

Three Phase Induction Motor MCQ Questions and Answers Page - 2

1.

In an induction motor, the air gap flux density is usually kept low so as to

Answer/ Hint      

Answer : B

Explanation :

2.

A wound rotor induction motor can be distinguished from squirrel cage induction motor by

Answer/ Hint      

Answer : A

Explanation :

3.

For induction motors normally

Answer/ Hint      

Answer : A

Explanation :

4.

A 3-phase , 4-squirrel cage indcutioni motor has 36 stator and 28 rotor slots. The number of phases in the rotor is

Answer/ Hint      

Answer : A

Explanation :

5.

The rotor slots are slightly skewed in  squirrel cage indcuiton mtor to

Answer/ Hint      

Answer : B

Explanation :

6.

Skewing of the rotor in a three phase squirrel cage induction motor redues

Answer/ Hint      

Answer : A

Explanation :

7.

The principle of operation of a 3-phase induction motor is almost smiliar to that of

Answer/ Hint      

Answer : C

Explanation :

8.

The rotor of a 3-phase induction motor rotates in the same direction as that of stator rotating field. This canbe explained by

Answer/ Hint      

Answer : B

Explanation :

9.

The relative speed between stator and rotor fluxes is equal to

Answer/ Hint      

Answer : C

Explanation :

10.

Stator flux induces emf in the rotor bar

Answer/ Hint      

Answer : C

Explanation :

11.

The 3-phse induction motor with  rotor circuit open will

Answer/ Hint      

Answer : C

Explanation :

12.

If any two leads from slip rings are interchanged in a 3-phase induction motor the motor will

Answer/ Hint      

Answer : A

Explanation :

13.

Two of the supply terminals to a 3-phase induction motor get interchanged during reconnection after normal maintenance , When switched on to supply the motor will

Answer/ Hint      

Answer : B

Explanation :

14.

The direction of rotation of a 3-phase induction motor canbe reversed by

Answer/ Hint      

Answer : A

Explanation :

15.

 The rotor of an induction motor rotates in the direction of the rotation of stator field in order to

Answer/ Hint      

Answer : A

Explanation :

16.

The rotor of an induction motor never runs at synchronous speed because then the relative speed between the rotating flux and rotor will be

Answer/ Hint      

Answer : D

Explanation :

17.

The voltage actually used for setting  of the useful flux I the air gap of 3-phase induction motor is

Answer/ Hint      

Answer : A

Explanation :

18.

Synchronous speed is defined as the speed at which the

Answer/ Hint      

Answer : A

Explanation :

19.

The maximum possible speed of a 3-phase squirrel cage induction motor running at a slip of 4% is

Answer/ Hint      

Answer : A

Explanation :

20.

The power factor of an induction motor under no-load conditions will be closer to

Answer/ Hint      

Answer : A

Explanation :

21.

The “clogging” of an induction motor can be avoided by

Answer/ Hint      

Answer : D

Explanation :

22.

If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as

Answer/ Hint      

Answer : C

Explanation :

23.

Slip of an induction motor is negative when

Answer/ Hint      

Answer : C

Explanation :

24.

Size of a high-speed motor as compared to low speed motor for the same H.P will be

Answer/ Hint      

Answer : B

Explanation :

25.

A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor will

Answer/ Hint      

Answer : A

Explanation :

26.

A 3-phase induction motor delta connected is carrying too heavy load and one of its fuses blows out. Then the motor

Answer/ Hint      

Answer : C

Explanation :

27.

Low voltage at motor terminals is due to

Answer/ Hint      

Answer : C

Explanation :

28.

In an induction motor the relationship between stator slots and rotor slots is that

Answer/ Hint      

Answer : C

Explanation :

29.

Slip ring motor is recommended where

Answer/ Hint      

Answer : D

Explanation :

30.

As load on an induction motor goes on increasing

Answer/ Hint      

Answer : D

Explanation :

31.

If a 3-phase supply is given to the stator and rotor is short circuited rotor will move

Answer/ Hint      

Answer : B

Explanation :

32.

It is advisable to avoid line starting of induction motor and use starter because

Answer/ Hint      

Answer : C

Explanation :

33.

The speed characteristics of an induction motor closely resemble the speed-load characteristics of which of the following machines

Answer/ Hint      

Answer : B

Explanation :

34.

Which type of bearing is provided in small induction motors to support the rotor shaft?

Answer/ Hint      

Answer : A

Explanation :

35.

A pump induction motor is switched on to supply 30% lower than its rated voltage. The pump runs. What will eventually happen? It will

Answer/ Hint      

Answer : D

Explanation :

36.

5 H.P, 50 Hz 3-phase, 440V, induction motors are available for the following r.p.m. which motor will be the costliest?

Answer/ Hint      

Answer : A

Explanation :

37.

A 3-phase slip ring motor has

Answer/ Hint      

Answer : B

Explanation :

38.

The torque developed in an induction motor is nearly proportional to

Answer/ Hint      

Answer : C

Explanation :

39.

Short-circuit test on an induction motor cannot be used to determine

Answer/ Hint      

Answer : A

Explanation :

40.

In a three-phase induction motor

Answer/ Hint      

Answer : D

Explanation :

41.

In case of 3-phase induction motors, plugging means

Answer/ Hint      

Answer : D

Explanation :

42.

Which of the following data is required to draw the circle diagram for an induction motor?

Answer/ Hint      

Answer : D

Explanation :

43.

In three-phase induction motors sometimes copper bars are placed deep in the rotor to

Answer/ Hint      

Answer : A

Explanation :

44.

In a three-phase induction motor

Answer/ Hint      

Answer : B

Explanation :

45.

The value of transformation ratio of an induction motor can be found by

Answer/ Hint      

Answer : B

Explanation :

46.

The power scale of circle diagram of an induction motor can be found from

Answer/ Hint      

Answer : C

Explanation :

47.

The shape of the torque / slip curve of induction motor is

Answer/ Hint      

Answer : C

Explanation :

48.

A change of 4% of supply voltage to an induction motor will produce a change of approximately

Answer/ Hint      

Answer : D

Explanation :

49.

The starting torque of the slip ring induction motor can be increased by adding

Answer/ Hint      

Answer : B

Explanation :

50.

A 500 KW, 3-phase ,440 volts, 50 HZ, A.C induction motor has as speed of 960 r.p.m on full load. The machine has 6 poles. The slip of the machine will be

Answer/ Hint      

Answer : D

Explanation :

51.

The complete circle diagram of induction motor can be drawn with help of data found from

Answer/ Hint      

Answer : D

Explanation :

52.

In the squirrel-cage induction motor the rotor slots are usually given slight skew

Answer/ Hint      

Answer : A

Explanation :

53.

The torque of a rotor in an induction motor under running conditions is maximum

Answer/ Hint      

Answer : C

Explanation :

54.

What will happen if the relative speed between the rotating flux of stator and rotor of an induction motor is zero?

Answer/ Hint      

Answer : B

Explanation :

55.

The circle diagram for an induction motor cannot be used to determine

Answer/ Hint      

Answer : A

Explanation :

56.

Blocked rotor test on induction motors is used to find out

Answer/ Hint      

Answer : D

Explanation :

57.

Lubricant used for ball bearing is aurally

Answer/ Hint      

Answer : B

Explanation :

58.

An induction motor can run at synchronous speed when

Answer/ Hint      

Answer : D

Explanation :

59.

Which motor is preferred for use in mines where explosive gases exist?

Answer/ Hint      

Answer : A

Explanation :

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