electrician

MCQ ON 3 - PHASE INDUCTION MOTOR PAGE - 2

1.

Thermal overload relays are _____than magnetic overload relays.

Answer/ Hint      

Answer : B

Explanation :

2.

Which of the following reduces vibration, chattering, noise, wear and heat in the armature of a starter?

Answer/ Hint      

Answer : B

Explanation :

3.

Minimum requirement of contacts in a 3 phase (d) O.L starter is :

Answer/ Hint      

Answer : A

Explanation :

4.

NVC used in a starter is meant to protect the motor against

Answer/ Hint      

Answer : D

Explanation :

5.

Full load line current of a 3 phase , 3H.P, 415 V, 50 Hz , squirrel cage inductionmotor is approximately:

Answer/ Hint      

Answer : B

Explanation :

6.

No-load current of an induction motor is approximately ______percent of full load current

Answer/ Hint      

Answer : C

Explanation :

7.

In a (d) O.L starter a NVC is connected across a phase and neutral of a 3-phase, 415 V, 50 Hz supply and it works normally. What is the rating of NVC?

Answer/ Hint      

Answer : B

Explanation :

8.

A (d) O.L starter can be used satisfactorily for a double cage squirrel cage induction motor upto

Answer/ Hint      

Answer : B

Explanation :

9.

The purpose of a backup fuse is to provide protection against

Answer/ Hint      

Answer : D

Explanation :

10.

A 4-pole, 3-phase, 50 Hz motor’s speed is 95 % of its synchronous speed then the actual speed of the motor is

Answer/ Hint      

Answer : D

Explanation :

11.

The induction motor of a pump is run at a supply voltage 30% lesser thanthe normal voltage (415V). The pump starts to work. After some time what possibly can happen?

Answer/ Hint      

Answer : A

Explanation :

12.

The purpose of adding a rheostat to slip ring induction motor is to

Answer/ Hint      

Answer : C

Explanation :

13.

The rotor current frequency of a slip-ring induction motor depends on

Answer/ Hint      

Answer : C

Explanation :

14.

When the rotor of a slip ring induction motor is standstill, the rotor frequency is

Answer/ Hint      

Answer : D

Explanation :

15.

If the load on a motor is increased beyond its full load point the greatest effect of the increase in slip is in

Answer/ Hint      

Answer : C

Explanation :

16.

Regarding skewing of motor bars in a squirrel cage induction motor (SCIM), which statement is false?

Answer/ Hint      

Answer : B

Explanation :

17.

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

Answer/ Hint      

Answer : C

Explanation :

18.

The effect of increasing the length of air gap in an induction motor will be to  increase the

Answer/ Hint      

Answer : C

Explanation :

19.

In a 3 phase induction motor, the relative speed of stator flux with  respect to ___ is zero

Answer/ Hint      

Answer : C

Explanation :

20.

A 3-phase, 4-pole, 50 Hz induction motor runs at a speed of 1440 R.P.M The rotating field produced by the rotor rotates at a speed of ____ R.P.M with respect to the rotor

Answer/ Hint      

Answer : C

Explanation :

21.

In a 3 phase induction motor, the rotor field rotates at synchronous speed with respect to

Answer/ Hint      

Answer : A

Explanation :

22.

Irrespective of the supply frequency, the torque developed by a SCIM is the same when ever_____is the same.

Answer/ Hint      

Answer : D

Explanation :

23.

The number of stator poles produced in the rotating  magnetic field of a 3-phase induction  motor  having three slots per pole per phase is

Answer/ Hint      

Answer : B

Explanation :

24.

The power factor of a squirrel cage induction motor is

Answer/ Hint      

Answer : A

Explanation :

25.

A 6 pole, 50 Hz, 3 phase induction motor is running at 950 R.P.M and has rotor copper loss of 5 KW. Its rotor input is _____KW

Answer/ Hint      

Answer : A

Explanation :

26.

The efficiency of a 3-phase induction motor is approximately proportional to

Answer/ Hint      

Answer : A

Explanation :

27.

A 6 pole, 50 Hz, 3 phase induction motor has a full load speed of 950 R.P.M. At half load, its speed would be ___R.P.M

Answer/ Hint      

Answer : C

Explanation :

28.

If rotor input of a SCIM running with a slip of 10% is 100 KW, gross power developed by its rotor is ______KW

Answer/ Hint      

Answer : B

Explanation :

29.

When applied rated voltage per phase is reduced by one half, the starting torque of a SCIM becomes ____of the starting torque with full voltage

Answer/ Hint      

Answer : B

Explanation :

30.

The fractional slip of an induction motor is the ratio of

Answer/ Hint      

Answer : A

Explanation :

<< Previous
MCQ ON 3 - PHASE INDUCTION MOTOR PAGE - 2
Next >>