Slip-rings in a synchronous motor carry____________?

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. The percentage slip in case of a synchronous motor is____________?

   A. 1%
   B. 100%
   C. 0.5%
   D. zero

3. Slip rings are usually made of__________?

   A. carbon or graphite
   B. brass or steel
   C. silver or gold
   D. copper or aluminium

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. A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

   A. synchronous motor has no slip
   B. stator supply is not required to produce magnetic field
   C. mechanical load on the rotor remains constant
   D. synchronous motor has large airgap

8. 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

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. 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