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

Related Mcqs:

1. In a synchronous motor, damper windings are provided on____________?

   A. stator frame
   B. rotor shaft
   C. pole faces
   D. none of the above

2. 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

3. When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor___________?

   A. remains same as the original value
   B. decreases to half the original value
   C. tends to becomes zero
   D. increases to two times the original value

4. Hunting in a synchronous motor cannot be due to___________?

   A. windage friction
   B. variable load
   C. variable frequency
   D. variable supply voltage

5. Under which of the following conditions hunting of synchronous motor is likely to occur?

   A. Periodic variation of load
   B. Over-excitation
   C. Over-loading for long periods
   D. Small and constant load

6. The rotor copper losses, in a synchronous motor, are met by____________?

   A. d.c. source
   B. armature input
   C. motor input
   D. supply lines

7. The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of_____________?

   A. zero degree
   B. two degrees
   C. five degrees
   D. ten degrees

8. The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as___________?

   A. pull-up torque
   B. pull-in torque
   C. pull-out torque
   D. none of the above

9. The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as__________?

   A. locked-rotor torque
   B. synchronous torque
   C. pull up torque
   D. reluctance torque

10. A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have_____________?

    A. no change of power factor
    B. lagging power factor with over-excitation
    C. leading power factor with under-excitation
    D. leading power factor with over-excitation