THREE PHASE INDUCTION MOTORS QUIZ

If a 3-phase induction motor is running at slip S, then rotor copper loss is equal to

S × rotor input

(1+S) × rotor input

(1-S) × rotor input

None of the listed here

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One of the speeds of a 2 speed squirrel cage induction motor is 800 rpm. The other speed will be _____

2400 rpm

1600 rpm

400 rpm

1200 rpm

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When a 3-phase induction motor is at no load, the slip is ______

1

0.5

0.2

Practically zero

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If a 3 phase induction motor is running at a slip S, then approximate efficiency of the motor is ______

None of the listed here

1+S

S-1

1-S

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The frame of an induction motor is usually made of

Silicon steel

Cast iron

Bronze

Aluminium

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For the same kVA rating, the leakage flux in induction motor is _______ that of transformer.

None of the listed here

More than

Less than

About the same

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The maximum torque in an induction motor depends on

Rotor inductive reactance

Square of supply voltage

Frequency

All of the listed here

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

Large

Absent

Infinity

Small

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

Star-delta starting

By auto transformer starting

None of the listed here

Direct on line

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In a squirrel cage induction motor, the number of rotor bars is generally ________

Prime number

Even number

None of the listed here

Equal to stator poles

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