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.Management Sciences
Category: Synchronous Motors
The minimum armature current of the synchronous motor corresponds to operation at______________?
A. zero power factor leading
B. unity power factor
C. 0.707 power factor lagging
D. 0.707 power factor leading
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 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
When the voltage applied to a synchronous motor is increased, which of the following will reduce?
A. Stator flux
B. Pull in torque
C. Both A. and (b)
D. None of the above
To limit the operating temperature an electrical machine should have proper____________?
A. voltage rating
B. current rating
C. power factor
D. speed
A synchronous motor working at leading power factor can be used as____________?
A. voltage booster
B. phase advancer
C. noise generator
D. mechanical synchronizer
In case one phase of a three-phase synchronous motor is short-circuited the motor will____________?
A. not start
B. run at 2/3 of synchronous speed
C. run with excessive vibrations
D. take less than the rated load
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
A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as_________?
A. static condenser
B. condenser
C. synchronous condenser
D. none of the above
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