Related Mcqs:

1. 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

2. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected______________?

   A. the motor stops
   B. it runs as a reluctance motor at the same speed
   C. it runs as a reluctance motor at a lower speed
   D. none of the above

3. While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by_____________?

   A. induction motor torque in field winding
   B. induction motor torque in damper winding
   C. eddy current and hysteresis torque in pole faces
   D. reHetance motor torque due to saliency of the rotor
   E. all of the above methods

4. 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

5. 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

6. While starting a synchronous motor by induction motor action, field winding is usually_____________?

   A. connected to D.C. supply
   B. short-circuited by low resistance
   C. kept open-circuited
   D. none of the above

7. 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

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

   A. will refuse to start
   B. will overheat in spots
   C. will not come upto speed
   D. will fail to pull into step

9. In a synchronous motor, the damping winding is generally used to______________?

   A. reduce noise level
   B. reduce the eddy currents
   C. provide starting torque only
   D. prevent hunting and provide the starting torque
   E. none of the above

10. If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is__________?

    A. 2
    B. 3
    C. 4
    D. 6