ELECTRICAL MACHINES QUIZ

Capacitor in split phase induction motor is used to

improve the power factor.

improve the starting torque.

reduce the harmonics.

start the motor.

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YOUR ANSWER : ?

In synchronous generator a synchronous dead load (lamp, furnaces etc) has no ____________ hence it has no natural frequency of oscillation.

synchronizing power co efficient.

damping torque.

restoring torque.

mechanical rotatory system.

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If the air gap of IM is increased, ____________ will increase.

power factor.

air gap flux.

speed.

magnetizing current.

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DC Motor

dc shunt motor with field weakening.

dc shunt with armature resistance control.

dc series motor.

dc compound motor.

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If a DC motor is connected across the AC supply it will

Burn.

Not run.

Run at lower speed.

Run at normal speed.

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YOUR ANSWER : ?

The back emf produced in a dc motor depends on

Z.

P.

none of these.

P and Z.

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The armature mmf of a DC machine has

trapezoidal space distribution and is stationary in space.

triangular space distribution and is stationary in space.

triangular space distribution and rotates at the speed of armature.

stepped distribution and rotates at the speed of armature.

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If peak value of phase mmf is F max , then peak value of the rotating field caused by three phase is

3Fmax.

(3/2)Fmax.

Fmax.

(1/2)Fmax.

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A dc shunt generator has full-load voltage regulation of 10% at rated speed of 1000 rpm. If it is now driven at 1250 rpm, then its voltage regulation at full load would

be more than 10%

be 12.5%

remain unchanged

be less than 10%

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In V/f speed control of 3-phase induction motor, with increase in frequency, the slip at which maximum torque occurs

increase.

None of these

either of these.

decrease.

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YOUR ANSWER : ?