The speed regulation of a synchronous motor is always___________?

Related Mcqs:

1. 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

2. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop_________________?

   A. inductor motor torque
   B. induction generator torque
   C. synchronous motor torque
   D. d.c. motor toque
   E. none of the above

3. 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

4. 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

5. 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

6. 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

7. An important advantage of a synchronous motor over wound round induction motor is that

   A. its power factor may be varied at will
   B. its speed is independent of supply frequency
   C. its speed may be controlled more easily
   D. none of the above

8. The power factor of a synchronous motor is better than that of induction motor because

   A. stator supply is relieved of responsibility of producing magnetic field
   B. mechanical load on the motor can be adjusted
   C. synchronous motor runs at synchronous speed
   D. synchronous motor has large air gap

9. 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

10. 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