Power Electronics Mcqs

Q:

Determine the loss in the snubber circuit, if C = 0.545 μF and supply is 200 V, 10 kHz.

A) 233 W B) 133 W
C) 333 W D) 233 W
 
Answer & Explanation Answer: B) 133 W

Explanation: Snubber loss Ps = (1/2) x C x V² x f = 133.1 W.

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5
Q:

TRIAC is used in

A) chopper B) speed control of induction machine
C) speed control of universal motor D) none of the mentioned
 
Answer & Explanation Answer: C) speed control of universal motor

Explanation: TRIAC is used in speed control of universal motor.

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7
Q:

A single-phase full bridge diode rectifier delivers power to a constant load current of 10 A. The average and rms values of the source currents will be respectively.

A) 5 A, 10 A B) 10 A, 10 A
C) 5 A, 5 A D) 10 A, 5A
 
Answer & Explanation Answer: B) 10 A, 10 A

Explanation: As the load current is continuous, Iavg = Irms = 10 A.

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5
Q:

For a SCR, conduction angle is 120° when average on-state current is 20 A. When the conduction angle is halved the earlier value, the on-state average current will be?

A) 5 A B) 40 A
C) 10 A D) 20 A
 
Answer & Explanation Answer: B) 40 A

Explanation: When the conduction angle is halved, the device will conduct twice then it was conducting earlier. Hence, I = 2x 20 = 40 A.

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8
Q:

The factors governing the induction heating are

A) resistivity B) relative permeability
C) magnetic field intensity D) all of the mentioned
 
Answer & Explanation Answer: D) all of the mentioned

Explanation: Induction heating depends on all of the above given factors.

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5
Q:

Induction heating is a ___________ type of heating

A) zero frequency B) high frequency
C) power frequency D) none of the mentioned
 
Answer & Explanation Answer: B) high frequency

Explanation: As eddy current is proportional to the square of the supply frequency, induction heating is a high frequency heating.

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6
Q:

The converter circuit which employs turn on and turn off when the voltage and/or current through the device is zero at the instant of switching is ____________

A) a conventional converter B) a resonant converter
C) a zero switching circuit D) none of the mentioned
 
Answer & Explanation Answer: B) a resonant converter

Explanation: Resonant converters are used to turn on and turn off when the voltage and/or current through the device is zero at the instant of switching.

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6
Q:

Solid State Relays (SSRs) have a

A) coil and contact arrangement B) optocoupler
C) scr D) none of the mentioned
 
Answer & Explanation Answer: B) optocoupler

Explanation: Coil and contact arrangement is used in mechanical relays, SSRs have a optocoupler which connects the control circuit to the power circuit via light sensitive devices.

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7