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MCQs 1: When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop_________________?

inductor motor torque induction generator torque synchronous motor torque d.c. motor toque none of the above
Answer Explanation

MCQs 2: While starting a synchronous motor by induction motor action, field winding is usually_____________?

connected to D.C. supply short-circuited by low resistance kept open-circuited none of the above
Answer Explanation

MCQs 3: Armature of a synchronous machine is____________?

of reducing number of slip rings on the rotor armature is associated with large power as compared to the field circuits of difficulty of providing high voltage insulation on rotor all of the above reasons
Answer Explanation

MCQs 4: The power factor of a synchronous motor is better than that of induction motor because

stator supply is relieved of responsibility of producing magnetic field mechanical load on the motor can be adjusted synchronous motor runs at synchronous speed synchronous motor has large air gap
Answer Explanation

MCQs 5: If one-phase of a 3-phase synchronous motor is short-circuited, motor will ______________?

will refuse to start will overheat in spots will not come upto speed will fail to pull into step
Answer Explanation

MCQs 6: The maximum speed variation in a 3-phase synchronous motor is____________?

10 per cent 6 per cent 4 per cent 2. per cent zero
Answer Explanation

MCQs 7: In a synchronous motor, the maximum power developed depends on all of the following except:

rotor excitation maximum value of coupling angle direction of rotation supply voltage
Answer Explanation

MCQs 8: The effect of increasing the load on a synchronous motor running with normal excitation is to___________?

decrease both armature current and power factor decrease armature current but increase power factor increase armature current but decrease power factor increase both its armature current and power factor
Answer Explanation

MCQs 9: In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on___________?

load on the motor d.c. excitation only both the speed and rotor flux none of the above
Answer Explanation

MCQs 10: Hunting in a synchronous motor cannot be due to___________?

windage friction variable load variable frequency variable supply voltage
Answer Explanation

MCQs 11: A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have_____________?

no change of power factor lagging power factor with over-excitation leading power factor with under-excitation leading power factor with over-excitation
Answer Explanation

MCQs 12: A synchronous motor develops maximum power when load angle is____________?

45° 60° 90° 120°
Answer Explanation

MCQs 13: The armature current of the synchronous motor

has large values for low excitation i niy has large values for high excitation only has large values for low and high excitation any of the above
Answer Explanation

MCQs 14: Exciters of synchronous machines are______________?

d.c. series machines d.c. shunt machines d.c. compound machines any of the above
Answer Explanation

MCQs 15: The duration of sudden snort-circuit test on a synchronous motor is usually about_____________?

one hour one minute one second none of the above
Answer Explanation

MCQs 16: The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as_____________?

slip torque pull-out torque breaking torque synchronising torque
Answer Explanation

MCQs 17: Which of the following motors is non-self starting ?

D.C. series motor synchronous motor Squirrel cage induction motor Wound round induction motor
Answer Explanation

MCQs 18: The magnitude of field flux in a 3-phase synchronous motor?

varies with power factor varies with speed varies with the load remains constant at all loads
Answer Explanation

MCQs 19: The ratio of starting torque to running torque in a synchronous motor is____________?

zero one two infinity
Answer Explanation

MCQs 20: The induced e.m.f. in a synchronous motor working on leading power factor will be_____________?

more than the supply voltage less than the supply voltage equal to the supply voltage None of these
Answer Explanation

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