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_____________?

Related Mcqs:

1. 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

2. 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

3. 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

4. The ratio of starting torque to running torque in a synchronous motor is____________?

   A. zero
   B. one
   C. two
   D. infinity

5. 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

6. 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

7. 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

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. 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

10. 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