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MCQs 1: Which of the following methods is used to start a synchronous motor?

Damper winding Star-delta starter Damper winding in conjunction with star-delta starter Resistance starter in the armature circuit
Answer Explanation

MCQs 2: In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately

one-third twice thrice six times nine times
Answer Explanation

MCQs 3: A synchronous machine with large air gap has______________?

a higher value of stability limit a small value of inherent regulation a higher synchronizing power which makes the machine less sensitive to load variations all of the above
Answer Explanation

MCQs 4: To limit the operating temperature an electrical machine should have proper____________?

voltage rating current rating power factor speed
Answer Explanation

MCQs 5: When the voltage applied to a synchronous motor is increased, which of the following will reduce?

Stator flux Pull in torque Both A. and (b) None of the above
Answer Explanation

MCQs 6: An over excited synchronous motor is used for____________?

fluctuating loads variable speed loads low torque loads power factor corrections
Answer Explanation

MCQs 7: Slip rings are usually made of__________?

carbon or graphite brass or steel silver or gold copper or aluminium
Answer Explanation

MCQs 8: A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

synchronous motor has no slip stator supply is not required to produce magnetic field mechanical load on the rotor remains constant synchronous motor has large airgap
Answer Explanation

MCQs 9: Synchronous motors are_____________?

not-self starting self-starting essentially self-starting none of the above
Answer Explanation

MCQs 10: Synchronsizing power of a synchronous machine is_____________?

direcly proportional to the synchronous reactance inversely proportional to the synchronous reactance equal to the synchronous reactance none of the above
Answer Explanation

MCQs 11: 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___________?

remains same as the original value decreases to half the original value tends to becomes zero increases to two times the original value
Answer Explanation

MCQs 12: When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is___________?

more less equal twice
Answer Explanation

MCQs 13: Riunting in a synchronous motor takes place___________?

when supply voltage fluctuates when load varies when power factor is unity motor is under loaded
Answer Explanation

MCQs 14: The percentage slip in case of a synchronous motor is____________?

1% 100% 0.5% zero
Answer Explanation

MCQs 15: When the field of a synchronous motor is under-excited, the power factor will be____________?

leading lagging unity zero
Answer Explanation

MCQs 16: The oscillations in a synchronous motor can be damped out by_______________?

maintaining constant excitation running the motor on leading power factors providing damper bars in the rotor pole faces oscillations cannot be damped
Answer Explanation

MCQs 17: A synchronous motor can operate at____________?

lagging power factor only leading power factor only unity power factor only lagging, leading and unity power factors
Answer Explanation

MCQs 18: If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is__________?

2 3 4 6
Answer Explanation

MCQs 19: The minimum armature current of the synchronous motor corresponds to operation at______________?

zero power factor leading unity power factor 0.707 power factor lagging 0.707 power factor leading
Answer Explanation

MCQs 20: Synchronous motor always runs at______________?

the synchronous speed less than synchronous speed more than synchronous speed none of the above
Answer Explanation

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