THREE PHASE INDUCTION MOTORS QUIZ

The advantage of wound rotor motor is that _______

External resistance can be inserted in the rotor circuit

It requires less maintenance

None of the listed here

It is inexpensive

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The stator of a three phase induction motor produces _______ magnetic field.

Alternating

None of the listed here

Steady

Rotating

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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

1-S

S-1

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The injected e.m.f. in the rotor of induction motor must have

The same frequency as the slip frequency

Zero frequency

High value for the satisfactory speed control

The same phase as the rotor e.m.f.

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The starting torque of a squirrel cage induction motor is

Slightly more than full load torque

Negligible

Low

Same as full load torque

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The number of slip rings on a squirrel cage induction motor is usually

None

Three

One

Two

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In induction motor, percentage slip depends on

None of these

Supply voltage

Supply frequency

Copper losses in motor

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The efficiency of an induction motor can be expected to be nearly

80 to 90%

95 to 98 %

99%

60 to 90%

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The rotor of induction motor

Always revolves in the direction of stator flux

Always revolves in the direction opposite to stator flux

None of the listed here

Insufficient data

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The no load speed of an induction motor depends on

Both supply frequency and number of poles

The supply frequency

The maximum flux/poles

The number of its poles

TRUE ANSWER : ?
YOUR ANSWER : ?

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