250+ TOP MCQs on Miscellaneous and Answers

Power Electronics Multiple Choice Questions on “Miscellaneous”.

1. Solid State Relays (SSRs) have a
A. coil and contact arrangement
B. optocoupler
C. scr
D. none of the mentioned
Answer: B
Clarification: 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.

2. 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: B
Clarification: 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.

3. Induction heating is a ___________ type of heating
A. zero frequency
B. high frequency
C. power frequency
D. none of the mentioned
Answer: B
Clarification: As eddy current is proportional to the square of the supply frequency, induction heating is a high frequency heating.

4. The factors governing the induction heating are
A. resistivity
B. relative permeability
C. magnetic field intensity
D. all of the mentioned
Answer: D
Clarification: Induction heating depends on all of the above given factors.

5. The reverse recovery time of a diode is trr = 3 μs and the rate of fall of the diode current (di/dt) = 30 A/μs. Determine the storage charge.
A. 145 μs
B. 135 μs
C. 0
D. none of the mentioned
Answer: B
Clarification: Storage charge = (1/2) x (di/dt) x (trr)2 = 135 μs.

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

7. 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: B
Clarification: As the load current is continuous, Iavg = Irms = 10 A.

8. TRIAC is used in
A. chopper
B. speed control of induction machine
C. speed control of universal motor
D. none of the mentioned
Answer: C
Clarification: TRIAC is used in speed control of universal motor.

9. The ratio Vrms/ Vdc is known as
A. Form factor
B. Ripple factor
C. Utilization factor
D. None of the mentioned
Answer: A
Clarification: Vrms/ Vdc = FF.

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

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