electrical

Three Phase Induction Motor MCQ Questions and Answers Page - 4

1.

In a 3-phase induction motor the maximum torque

Answer/ Hint      

Answer : A

Explanation :

2.

For a slip ring induction motor, if the rotor resistance is increased then

Answer/ Hint      

Answer : C

Explanation :

3.

An induction motor has a rotor resistance of 0.002 ohm/ phase. If the resistance is increased to 0.004 ohm/phase then the maximum torque will

Answer/ Hint      

Answer : D

Explanation :

4.

Breakdown torque of a 3-phase induction motor of negligible stator impedance is

Answer/ Hint      

Answer : D

Explanation :

5.

A 4 – pole, 50 Hz, 3-phase induction motor has blocked rotor reactance per phase which is four times the rotor resistance per phase. The speed at which maximum torque develops is

Answer/ Hint      

Answer : A

Explanation :

6.

If the rotor circuit resistance is increased in an induction motor, the maximum torque will occur at

Answer/ Hint      

Answer : A

Explanation :

7.

Beyond the point of maximum torque any further increase in loads will cause

Answer/ Hint      

Answer : C

Explanation :

8.

The torque-slip characteristic of a polyphase induction motor becomes almost linear at small values of slip, because in this range of slips

Answer/ Hint      

Answer : A

Explanation :

9.

The torque –slip characteristic of an induction motor is approximately a/an

Answer/ Hint      

Answer : B

Explanation :

10.

Stable operation of an induction motor is

Answer/ Hint      

Answer : C

Explanation :

11.

with the increase in load on a squirrel cage induction motor

Answer/ Hint      

Answer : D

Explanation :

12.

Whenever polyphase induction motor is loaded

Answer/ Hint      

Answer : D

Explanation :

13.

In a 3-phase induction motor iron loss mainly occurs in

Answer/ Hint      

Answer : C

Explanation :

14.

Iron loss in the rotor of a 3-kphase induction motor is negligible This is due to

Answer/ Hint      

Answer : A

Explanation :

15.

Rotor input of a three-phase induction motor is equal to

Answer/ Hint      

Answer : A

Explanation :

16.

In an induction motor, what is the ratio of rotor copper loss and rotor input?

Answer/ Hint      

Answer : B

Explanation :

17.

The rotor power output of a 3-phase induction motor is 15 kW The rotor copper losses at a slip of 4% will be

Answer/ Hint      

Answer : B

Explanation :

18.

The synchronous watt is

Answer/ Hint      

Answer : A

Explanation :

19.

The no load current in an induction motor is ____in comparison to that of a power transformer.

Answer/ Hint      

Answer : B

Explanation :

20.

In a 3-phase induction motor, the variable mechanical load is represented electrically by a variable ____only

Answer/ Hint      

Answer : C

Explanation :

21.

If the load on an induction motor is increased from no load to full load, its slip and the power factor will, respectively

Answer/ Hint      

Answer : D

Explanation :

22.

The output power of a 3-phase induction motor will be maximum when the equivalent load resistant is equal to the standstill leakage _____of the motor

Answer/ Hint      

Answer : A

Explanation :

23.

The power factor of an induction motor operating at no load will have a value around

Answer/ Hint      

Answer : C

Explanation :

24.

The power factor of an induction motor at full load is likely to be

Answer/ Hint      

Answer : C

Explanation :

25.

Out of the following methods of staring a 3-phase induction motor, which one requires six stator terminals?

Answer/ Hint      

Answer : B

Explanation :

26.

If a single-phasing occurs on the running position in an induction motor, the motor will

Answer/ Hint      

Answer : D

Explanation :

27.

The fractional slip of an induction motor is the ratio

Answer/ Hint      

Answer : B

Explanation :

28.

Each of the following statements regarding stator flux of an induction motor is true expect

Answer/ Hint      

Answer : B

Explanation :

29.

The rotor of an induction motor cannot run with synchronous speed because

Answer/ Hint      

Answer : C

Explanation :

30.

When the load on a squirrel-cage induction motor is increased from no-load to full-load, which of the following statement is incorrect?

Answer/ Hint      

Answer : B

Explanation :

31.

The power factor of an induction motor under no-load conditions is about

Answer/ Hint      

Answer : A

Explanation :

32.

A pump induction motor is switched on to a supply 25 percent lower than its rated voltage. The pump runs eventually

Answer/ Hint      

Answer : A

Explanation :

33.

If there is an open circuit in the rotor of a squirrel cage induction motor

Answer/ Hint      

Answer : D

Explanation :

34.

The principle of operation of 3-phase induction motor is most similar to that of

Answer/ Hint      

Answer : A

Explanation :

35.

The speed of a 3-phase wound motor can be increased by

Answer/ Hint      

Answer : D

Explanation :

36.

The A.C motor which would be best suited to drive a centrifugal pump for discharging a variable quantity of water against a fixed head is the

Answer/ Hint      

Answer : D

Explanation :

37.

For staring a Schrage motor, 3-phase supply is connected to

Answer/ Hint      

Answer : A

Explanation :

38.

The primary winding of a Schrage motor is located

Answer/ Hint      

Answer : B

Explanation :

39.

When a stationary and partly in rotor motor is switched on with one phase disconnected

Answer/ Hint      

Answer : D

Explanation :

40.

The upper bars in a double squirrel cage induction motor have

Answer/ Hint      

Answer : C

Explanation :

41.

The pull-out torque for a normal squirrel cage induction motor usually occurs at a percentage slip of about

Answer/ Hint      

Answer : B

Explanation :

42.

Speed variations of a squirrel cage induction motor are essentially similar to those of

Answer/ Hint      

Answer : A

Explanation :

43.

If air gap of an induction motor is increased, its

Answer/ Hint      

Answer : C

Explanation :

44.

Two of the power supply terminals to a 3-phase induction motor get interchanged during reconnection after maintenance of the motor. When put back into service, the motor will be

Answer/ Hint      

Answer : D

Explanation :

45.

In three-phase induction motor, the relative speed of stator flux with respect to ……………. is zero

Answer/ Hint      

Answer : D

Explanation :

46.

In a 3-phase induction motor reactance under running conditions is less than its standstill value because of decrease in

Answer/ Hint      

Answer : D

Explanation :

47.

In case of a 3-phase wound-rotor induction motor, an increase in rotor resistance affects the motor performance in the following ways

Answer/ Hint      

Answer : C

Explanation :

48.

A squirrel cage induction motor running on no-load is loaded, which of the following statements is incorrect?

Answer/ Hint      

Answer : A

Explanation :

49.

Which of the following statement about 3-phase induction motor is incorrect?

Answer/ Hint      

Answer : A

Explanation :

50.

Which of the following statements about a double squirrel cage induction motor is incorrect?

Answer/ Hint      

Answer : B

Explanation :

51.

When a double squirrel cage motor is started, the current induced in the rotor

Answer/ Hint      

Answer : A

Explanation :

52.

Regarding single phase of a 3-phase induction motor under running conditions which of the following statements is incorrect?

Answer/ Hint      

Answer : A

Explanation :

53.

The difference between the synchronous speed and actual speed of an induction motor is known as

Answer/ Hint      

Answer : C

Explanation :

54.

In a induction motor if P is the power delivered to a rotor and s is the slip, then the power lost in the rotor as copper loss will be

Answer/ Hint      

Answer : B

Explanation :

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