ELECTRICAL MACHINES QUIZ

When an electric train is moving down a hill, the DC motor will operate as

DC series generator.

DC series motor.

DC shunt motor.

DC shunt generator.

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In an auto-transformer, power is transferred through

induction process only.

both A and B.

conduction process only.

None of these

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In travelling cranes for hoisting and lowering which type of motor is preferred?

AC slip ring motor.

Single phase induction motor.

Synchronous motor.

DC series motor.

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In salient pole synchronous machine, if direct axis reactance and quadrature axis reactance is equal, then power developed due to reluctance is

infinite value

any of the above

zero

maximum

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The armature core of the rotor bars of dc motors are laminated

to reduce mechanical losses.

to reduce eddy current loss.

to reduce hysteresis loss.

to provide better flux linkage.

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What is power factor of a 3 - φ induction motor at no load?

Same as full load.

Equal to 1.

Low.

High.

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If an induction machine is run at above the synchronous speed it acts as

an induction generator

an induction motor

None of these

a synchronous motor

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The stator frame in an induction motor is used to

provide return path for the flux.

ventilate the armature.

protect the whole machine.

hold armature stamping in position.

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Regenerative braking is not found in which motor?

DC shunt.

Induction motor.

DC series.

DC compound.

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The oscillation in a synchronous motor can be damped out by

providing damper bars in the rotor pole faces.

running the motor on leading power factors.

maintaining constant excitation.

oscillation cannot be damped.

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