If one-phase of a 3-phase synchronous motor is short-circuited, motor will ______________?

Related Mcqs:

1. In case one phase of a three-phase synchronous motor is short-circuited the motor will____________?

   A. not start
   B. run at 2/3 of synchronous speed
   C. run with excessive vibrations
   D. take less than the rated load

2. A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will___________?

   A. remain same
   B. go down
   C. improve
   D. none of the above

3. If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will__________?

   A. stop
   B. run as induction motor
   C. function as static condenser
   D. burn with dense smoke

4. In a 3-phase synchronous motor, the negative phase sequence exists when the motor is_______________?

   A. supplied with unbalanced voltage
   B. under-loaded
   C. over-loaded
   D. none of the above

5. If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then

   A. it runs at a slower speed
   B. the motor stops
   C. it continues to run at the same speed
   D. it runs at a very high speed

6. In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be____________?

   A. 3000 r.p.m.
   B. 1500 r.p.m.
   C. 750 r.p.m.
   D. none of the above

7. 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

8. A synchronous motor can develop synchronous torque:

   A. when under loaded
   B. while over-excited
   C. only at synchronous speed
   D. below or above synchronous speed

9. The magnitude of field flux in a 3-phase synchronous motor?

   A. varies with power factor
   B. varies with speed
   C. varies with the load
   D. remains constant at all loads

10. The maximum speed variation in a 3-phase synchronous motor is____________?

    A. 10 per cent
    B. 6 per cent
    C. 4 per cent
    D. 2. per cent
    E. zero