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MCQ ON 3 - PHASE INDUCTION MOTOR PAGE - 3

1.

The torque developed  by a 3-phase induction  motor depends on the following three factors

Answer/ Hint      

Answer : D

Explanation :

2.

The efficiency and power factor of a SCIM increase in proportion to its

Answer/ Hint      

Answer : B

Explanation :

3.

If the stator voltage and frequency of an induction motor are reduced proportionality, its

Answer/ Hint      

Answer : D

Explanation :

4.

An induction motor has  a shaft circuit current 7 times the fullload current and a full load slip of 4 percent. It s line starting is ____times the full load torque.

Answer/ Hint      

Answer : B

Explanation :

5.

If stator voltage of a SCIM is reduced to 50 percent of its rated value, torque developed is reduced by ____percent of its full load value.

Answer/ Hint      

Answer : C

Explanation :

6.

A SCIM with 36- slot stator has two separate windings one with 3 coil roups per phase per pole and the other with 2 coil grops per phase per pole. The obtainable two motor speeds would be in the ra

Answer/ Hint      

Answer : A

Explanation :

7.

A 6 pole, 3-phase induction motor taking 25 KW from a 50 Hz supply is cumulatively cascaded to a 4 pole motor, Neglecting all losses, speed of the 4 pole motor would be ____R.P.M

Answer/ Hint      

Answer : C

Explanation :

8.

Mark the WRONG statement

Schrage motor is capable of behaving as

Answer/ Hint      

Answer : D

Explanation :

9.

When  a stationary 3 phase induction motor is switched on with one phase disconnected

Answer/ Hint      

Answer : A

Explanation :

10.

If single phasing of a 3 phase induction motor occurs under the running condition, it

Answer/ Hint      

Answer : C

Explanation :

11.

If single phasing occurs during the running of a 3 phase motor, what is the effect on motor performance?

Answer/ Hint      

Answer : C

Explanation :

12.

You have to change the defective induction motor of a machine. The available motor is of a higher capacity than the existing one. What is the effect of using a higher capacity motor?

Answer/ Hint      

Answer : C

Explanation :

13.

The synchronous speed of an induction motor refers to the speed of the ….

Answer/ Hint      

Answer : C

Explanation :

14.

The synchronous speed formula is :

Answer/ Hint      

Answer : A

Explanation :

15.

Calculate slip of an induction motor if it has 4 poles, 50 Hz, rotor speed si 1400 rpm

Answer/ Hint      

Answer : A

Explanation :

16.

In a 3-phase motor the rotating magnetic filed is displaced at an angle of …

Answer/ Hint      

Answer : D

Explanation :

17.

Which one of the following 3-phase motor is NOT self-starting?

Answer/ Hint      

Answer : A

Explanation :

18.

The motor suitable for loads where constant speed is required is

Answer/ Hint      

Answer : A

Explanation :

19.

The magnetic field produced in the stator of a three-phase induction motor travel at

Answer/ Hint      

Answer : C

Explanation :

20.

For a small capacity induction motor, the type of starter used is….

Answer/ Hint      

Answer : B

Explanation :

21.

In a 3-phase induction motor started by a DOL starter, the short circuit current is protected by…

Answer/ Hint      

Answer : C

Explanation :

22.

It is advisable to avoid direct on line starting of induction motor having a capacity of more than 3HP because

Answer/ Hint      

Answer : B

Explanation :

23.

On switching ON the starter the magnetic contactor vibrates heavityly , the causes may be…

Answer/ Hint      

Answer : D

Explanation :

24.

In the manual star delta starter, the stop button connection is in series with the

Answer/ Hint      

Answer : B

Explanation :

25.

You are working with a fully automatic star delta starter. You notice that when start switch is pressed the motor starts in star, but does not change to delta. In the above case, the trouble will b

Answer/ Hint      

Answer : B

Explanation :

26.

A 3-phase 15HP, 415 V, 50Hz squirrel cage motor’s star delta starter cables are found to be defective copper cables are replaced by same current capacity aluminium cables through the same met

Answer/ Hint      

Answer : C

Explanation :

27.

Rotor resistance starters are used with wound rotor induction mtor. When the motor is running the resistance in starter are

Answer/ Hint      

Answer : A

Explanation :

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