SYNCHRONOUS MOTORS QUIZ

Hunting in a synchronous motor cannot be due to

variable load

variable supply voltage

variable frequency

windage friction

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Mostly, synchronous motors are of

Salient pole type machines

Alternator type machines

Induction type machines

Smooth cylindrical type machines

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The pull out torque of a synchronous motor will ______ as the field excitation is increased.

Increase

None of the listed here

Decrease

Remain unchanged

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The maximum speed variation in a 3 phase synchronous motor is

Zero

10 percent

2 percent

4 percent

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If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then

the back e.m.f. will be more than the supply voltage

the stator current will be very small

the stator current will be very high

the stator current will be zero

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A synchronous motor will always stop when

Load in motor varies

Supply voltage frequency changes

Supply voltage fluctuates

Excitation winding gets disconnected

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An important advantage of a synchronous motor over wound round induction motor is that

its power factor may be varied at will

None of these

its speed is independent of supply frequency

its speed may be controlled more easily

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The minimum armature current of the synchronous motor corresponds to operation at

zero power factor leading

unity power factor

0.707 power factor leading

0.707 power factor lagging

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The back emf in the stator of a synchronous motor depends on

Rotor excitation

Rotor speed

None of the listed here

Flux density

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The pull out torque of a synchronous motor is generally ______ times its full-load torque.

5 to 10

1.25 to 3.5

6 to 9

0.5

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