THREE PHASE INDUCTION MOTORS QUIZ

The good power factor of an induction motor can be achieved if the average flux density in the air gap is

Infinity

Large

Absent

Small

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For higher efficiency of 3-phase induction motor, the slip should be

As small as possible

Large

1

Very large

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Very large 3-phase induction motors (greater than 25 HP) are started _____

By auto transformer starting

None of the listed here

Star-delta starting

Direct on line

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In a 3 phase induction motor, the rotor speed is _____ the synchronous speed.

Equal to

Greater than

None of the listed here

Smaller than

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Slip rings are usually made of

Phospor bronze

Copper

Carbon

Aluminium

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In an induction motor if air gap increased

Bearing friction will reduce

Windage losses will be more

The power factor will be low

Copper loss will reduce

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The rotor winding of a 3phase wound rotor induction motor is generally _______ connected.

None of the listed here

Delta

Partly star and partly delta

Star

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The shaft of induction motor is made of

Stiff

Flexible

Any of the listed here

Hollow

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The crawling in an induction motor is caused by

High loads

Low voltage supply

Improper design of machine

Harmonics developed in the rotor

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The 3- phase induction motor is so designed that the rotor should have ______ under running conditions.

Low resistance

high resistance

Large slip

High reactance

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