Synchronous motor always runs at______________?

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 minimum armature current of the synchronous motor corresponds to operation at______________?

   A. zero power factor leading
   B. unity power factor
   C. 0.707 power factor lagging
   D. 0.707 power factor leading

3. 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

4. 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

5. A synchronous motor will always stop when:______________?

   A. supply voltage fluctuates
   B. load in motor varies
   C. excitation winding gets disconnected
   D. supply voltage frequency changes

6. 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

7. 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

8. As the load is applied to a synchronous motor, the motor takes more armature current because

   A. the increased load has to take more current
   B. the rotor by shifting its phase backward causes motor to take more current
   C. the back e.m.f. decreases causing an increase in motor current
   D. the rotor strengthens the rotating field casuing more motor current

9. A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

   A. power factor as well as armature current will decrease
   B. power factor as well as armature current will increase
   C. power factor will increase but armature current will decrease
   D. power factor will decrease and armature current will increase

10. 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