Electrical Machines Multiple Choice questions

MCQs on Electrical Machines

1. If field current is decreased in shunt dc motor, the speed of the motor

remains same.
none of the above.

2. What is the mechanical power developed by a DC series motor is maximum?

Back emf is equal to half the applied voltage.
Back emf is equal to applied voltage.
Back emf is equal to zero.
None of above.

3. What is the shunt resistance component equivalent circuit obtained by no load test of an induction motor representative of ?

windage and friction loss
core loss only
both 1 and 2
Copper loss

4. In Ward-Leonard system, the lower limit of the speed imposed by

Field resistance.
Armature resistance.
Residual magnetism of the generator.
None of above.

5. Ward-Leonard control is basically a ___________ control method.

Field control.
Armature resistance control.
Armature voltage control.
Field diverter control.

6. For very sensitive and wide speed control, the preferable control method is

Armature control.
Ward-Leonard control
Multiple voltage control.
Field control.

7. Eddy current loss will depends on

Flux density
All of the above

8. Hysteresis loss will depends on


9. Thin laminations are used in a machine in order to reduce

Eddy current losses
Hysteresis losses
Both 1 and 2
Copper losses

10. Hysteresis loop represents the area of

copper loss
eddy current loss
hysteresis loss
total iron losses