Synchronous motor. Part – 1

1. A three phase synchronous motor will have

A. No slip rings

B. Two slip rings

C. One slip rings

D. Three slip rings

2. A synchronous motor can be used as a synchronous capacitor when it is

A. Under loaded

B. Over loaded

C. Under excited

D. Over excited

3. Synchronous motors are generally not self starting because

A. The direction of rotation is not fixed

B. The direction of instantaneous torque reverser after half cycle

C. Starters can not be used on these machine

D. Starting winding is not provided on the machine

4. The number of poles of a synchronous motor is ‘8’ if the motor is connected to a 50 Hz AC supply, the speed of motor will be,

A. 1500rpm

B. 1000rpm

C. 750rpm

D. 3000rpm

5. If the excitation (field current) of a synchronous motor is increased to a large value its power factor will be,

A. Lagging

B. Leading

C. Zero

D. None of these

6. Synchronous motor can operate at

A. Leading power factor only

B. Unity power factor only

C. Lagging power factor only

D. Lagging, leading and unity power factor only

7. In case the field of a synchronous motor is under excited, the power factor will be

A. Zero

B. Leading

C. Unity

D. lagging

8. In 3-phase synchronous motor hunting is prevented by

A. Dummy coils

B. Compensating winding

C. Damper winding

D. Short-pitch winding

9. An induction motor and synchronous motor are connected to a common feeder line, to operate the feeder line at unity pf, the synchronous motor should be

A. under excited

B. over excited

C. normally excited

D. disconnected from the common terminals

10. An over-excited synchronous motor behaves as

A. A resistor

B. An inductor

C. A capacitor

D. None of the above