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

Related Mcqs:

1. 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

2. The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as_____________?

   A. slip torque
   B. pull-out torque
   C. breaking torque
   D. synchronising torque

3. 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

4. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

   A. High field current
   B. Low short circuit ratio
   C. High core losses
   D. Low field current

5. 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

6. If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor__________?

   A. become more
   B. become less
   C. remain constant
   D. none of the above

7. If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor

   A. will become more
   B. will become less
   C. will remain unchanged
   D. none of the above.

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

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

9. 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

10. 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