A. the direction of rotation is not fixed
B. the direction of instantaneous torque reverses after half cycle
C. startes cannot be used on these machines
D. starting winding is not provided on the machines
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 - Which of the following motors is non-self starting ?
A. D.C. series motor
B. synchronous motor
C. Squirrel cage induction motor
D. Wound round induction motor - 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 - 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 - The standard full-load power factor ratings for synchronous motors are___________?
A. zero or 0.8 leading
B. unity or 0.8 lagging
C. unity or 0.8 leading
D. unity or zero - 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 - Mostly, synchronous motors are of_____________?
A. alternator type machines
B. induction type machines
C. salient pole type machines
D. smooth cylindrical type machines - Synchronous motors are_____________?
A. not-self starting
B. self-starting
C. essentially self-starting
D. none of the above - For power factor correction, synchronous motors operate at____________?
A. no-load and greatly over-excited fields
B. no-load and under-excited fields
C. normal load with minimum excitation
D. normal load with zero excitation
