A. connected to D.C. supply
B. short-circuited by low resistance
C. kept open-circuited
D. none of the above
Related Mcqs:
- 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 - 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 - 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 - 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 - 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 - 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 - In a synchronous motor, the damping winding is generally used to______________?
A. reduce noise level
B. reduce the eddy currents
C. provide starting torque only
D. prevent hunting and provide the starting torque
E. none of the above - The synchronous motor is not inherently self-starting because_______________?
A. the force required to accelerate the rotor to the synchronous speed in an instant is absent
B. the starting device to accelerate the rotor to near synchronous speed is absent
C. a rotating magnetic field does not have enough poles
D. the rotating magnetic field is produced by only 50 Hz frequency currents - The ratio of starting torque to running torque in a synchronous motor is____________?
A. zero
B. one
C. two
D. infinity - A synchronous motor can be made self starting by providing?
A. damper winding on rotor poles
B. damper winding on stator
C. damper winding on stator as well as rotor poles
D. none of the above
