30 SEPTEMBER 2021 CURRENT AFFAIRS QUIZ

Hunting in a synchronous motor can not be due to

Variable supply frequency

Variable frequency

Windage friction

Variable load

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The standard full-load power factor ratings for synchronous motors are

unity or zero

zero or 0.8 leading

unity or 0.8 lagging

unity or 0.8 leading

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A synchronous motor delivers reactive power when ______

None of the listed here

Normally excited

Under excited

Over excited

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In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then

the motor is said to be fully loaded

the excitation is said to be hundred per cent

the excitation is said to be zero per cent

the torque generated is maximum

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Synchronous motors are generally used in application requiring _______

Frequent stopping

Sudden application of heavy loads

Variable speed

Infrequent starting

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The magnitude of field flux in a 3-phase synchronous motor

Remains constant at all loads

Varies with speed

Varies with the load

Varies with power factor

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In a synchronous motor, the forced vibrations will be maximum when driving

Any of the listed here

A centrifugal pump

A reciprocating air compressor

A centrifugal blower

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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

twice

equal

less

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The speed of a synchronous motor

None of the listed here

Decreases as the load decreases

Increases as the load increases

Always remains constant

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The armature current of the synchronous motor has higher values for

Both higher and low excitation

Higher excitation only

Low excitation only

None of the listed here

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