Electrical Machines Multiple Choice Questions and Answers

1. The power factor of the induction motor will be __________ if the magnetizing current is __________

1. Low......low
2. High........high
3. High.....low
4. Low ....... high

2. The magnetizing current of an induction motor will be __________ for __________ air gap

1. Larger .......... smaller
2. Larger ......... larger
3. Smaller....... larger
4. Smaller...........smaller

3. In induction motors, small air gap __________ power factor and __________ noise level

1. Increases .......... reduces
2. Reduces .......... increases
3. Reduces..........also reduces
4. Increases..........also increases

4. In induction motors, the difference between the number of stator and rotor slots should not be

1. P
2. 2P
3. 5P
4. Any of the above

5. Induction motor which of the following depends on the leakage reactance?

1. Starting torque
2. Maximum torque
3. Starting current
4. All of the above

6. The use of double squirrel cage winding on the rotor provides

1. Low noise
2. Reduced starting torque
3. A large starting torque
4. Higher efficiency

7. In induction motor if the number of rotor slots is equal to the stator slots then

1. The motor will run smoothly
2. The motor will mil at zero slip
3. The noise level will be low
4. The motor may refuse to start

8. In squirrel cage motors, skin effect occurs in

1. Stator winding
2. Rotor winding
3. Both (A) and (B) above
4. None of the above

9. A synchronous machine having large length of the air gap will have

1. Higher noise level
2. Smaller unbalanced magnetic pull
3. Lower limit of stability
4. Higher value of inherent regulation

10. Damper windings are provided in synchronous machines to

1. Damp out rotor oscillations
2. Reduce the over-voltages under abnormal conditions
3. Facilitate starting
4. All of the above