Power Electronics MCQs

1. In a single-phase full-bridge rectifier, the frequency of output voltage ripple is: A. Twice the input frequency
B. Equal to the input frequency
C. Half of the input frequency
D. Four times the input frequency
Answer: A

2. The device used for switching in a buck converter is typically: A. Thyristor
B. Diode
C. MOSFET
D. BJT
Answer: C

3. In a DC chopper circuit, if the duty cycle of the switch is 0.6, the average output voltage is: A. 0.6 times the input voltage
B. 0.4 times the input voltage
C. Equal to the input voltage
D. Dependent on the load resistance
Answer: A

4. The main advantage of using an IGBT over a MOSFET in power electronics applications is: A. Higher efficiency
B. Lower conduction losses
C. Lower gate drive power
D. Better thermal stability
Answer: B

5. A freewheeling diode is used in a: A. Buck converter
B. Boost converter
C. Flyback converter
D. Half-bridge inverter
Answer: C

6. The purpose of a snubber circuit in power electronics is to: A. Improve efficiency
B. Protect the switch from voltage spikes
C. Reduce electromagnetic interference (EMI)
D. Improve power factor
Answer: B

7. The power factor of a fully controlled bridge rectifier (with resistive load) operating at firing angle α is: A. Cos(α)
B. Sin(α)
C. 1
D. Zero
Answer: A

8. A cycloconverter converts: A. AC to DC
B. DC to AC
C. AC of one frequency to AC of another frequency
D. AC to higher voltage AC
Answer: C

9. In a three-phase full-bridge inverter, each thyristor or IGBT is fired: A. Alternately
B. In a sequence determined by the control logic
C. Only during the positive half cycle of the AC supply
D. Based on the zero-crossing of the load current
Answer: B

10. A step-up chopper is used when: A. Output voltage is lower than input voltage
B. Output voltage is higher than input voltage
C. Output current is higher than input current
D. Output current is lower than input current
Answer: B

11. The snubber circuit across a power electronic switch is used to: A. Provide additional power to the load
B. Protect the switch from voltage spikes
C. Smooth out the output voltage
D. Increase the efficiency of the switch
Answer: B

12. The function of a freewheeling diode in a controlled rectifier is to: A. Prevent reverse voltage across the diode
B. Short-circuit the load during the off-state of the thyristor
C. Provide additional current during high load conditions
D. Smooth out the output voltage
Answer: A

13. The firing angle of a thyristor in a single-phase half-wave rectifier is 30 degrees. The average output voltage is: A. 0.5 times the peak input voltage
B. 0.866 times the peak input voltage
C. 0.707 times the peak input voltage
D. 0.866 times the RMS input voltage
Answer: B

14. In a PWM inverter, the width of the PWM pulses remains constant, and the: A. Amplitude of the pulses varies
B. Frequency of the pulses varies
C. Duty cycle of the pulses varies
D. None of the above
Answer: A

15. Which of the following is true about the output voltage waveform of a half-wave rectifier? A. It is a complete sine wave
B. It is a series of half sine waves
C. It is a series of pulses
D. It is a constant DC voltage
Answer: B

16. In a three-phase bridge rectifier, the average DC output voltage is approximately: A. 0.9 times the peak line-to-line AC voltage
B. 0.6 times the peak line-to-line AC voltage
C. Equal to the peak line-to-line AC voltage
D. Twice the peak line-to-line AC voltage
Answer: A

17. Which of the following devices has the highest switching speed? A. MOSFET
B. Thyristor
C. IGBT
D. Diode
Answer: A

18. The power electronics device that combines the high input impedance of MOSFETs and the low on-state power losses of bipolar junction transistors is called: A. Thyristor
B. IGBT
C. Diac
D. TRIAC
Answer: B

19. The primary function of a snubber circuit in a power electronic circuit is to: A. Provide protection against overvoltage
B. Minimize electromagnetic interference (EMI)
C. Improve efficiency
D. Limit the rate of change of current
Answer: A

20. A unidirectional device that allows current to flow in only one direction and blocks current in the reverse direction is called: A. Diode
B. Triode
C. IGBT
D. JFET
Answer: A

21. In a buck-boost converter, the output voltage is: A. Always higher than the input voltage
B. Always lower than the input voltage
C. Sometimes higher and sometimes lower than the input voltage
D. Equal to the input voltage
Answer: C

22. The main advantage of a resonant converter over a traditional PWM converter is: A. Higher efficiency
B. Lower cost
C. Simpler control
D. Smaller size
Answer: A

23. Which of the following topologies is commonly used for grid-tied solar inverters? A. H-bridge
B. Flyback converter
C. Boost converter
D. Half-bridge
Answer: A

24. The voltage drop across a conducting thyristor or IGBT when it is in the on-state is called: A. Forward voltage drop
B. Reverse recovery voltage
C. Breakdown voltage
D. Leakage voltage
Answer: A

25. Which of the following is a disadvantage of using MOSFETs in high-power applications compared to IGBTs? A. Higher switching losses
B. Lower input impedance
C. Greater conduction losses
D. More complex gate drive requirements
Answer: C

26. The main function of a snubber circuit in a power electronic switch is to: A. Protect the switch from overvoltage
B. Provide gate drive to the switch
C. Increase the switching speed
D. Limit the rate of change of current
Answer: A

27. A rectifier converts: A. DC to AC
B. AC to DC
C. AC of one frequency to AC of another frequency
D. AC to higher voltage AC
Answer: B

28. In a single-phase half-wave rectifier, if the load resistance is doubled, the output DC voltage will: A. Remain the same
B. Double
C. Halve
D. Quadruple
Answer: B

29. A step-up chopper is used to: A. Decrease the output voltage
B. Increase the output voltage
C. Decrease the output current
D. Increase the output current
Answer: B

30. In a three-phase full-wave rectifier, the output voltage ripple frequency is: A. Equal to the input frequency
B. Twice the input frequency
C. Three times the input frequency
D. Six times the input frequency
Answer: B

31. The term ‘commutation’ in power electronics refers to: A. The process of turning off a semiconductor device
B. The process of turning on a semiconductor device
C. The process of converting AC to DC
D. The process of changing the frequency of AC voltage
Answer: A

32. The output waveform of a buck converter is: A. Rectangular
B. Sinusoidal
C. Triangular
D. None of the above
Answer: A

33. Which of the following is a disadvantage of a flyback converter? A. Simple circuit design
B. High electromagnetic interference (EMI)
C. Low voltage conversion ratio
D. High efficiency
Answer: B

34. The term ‘chopping’ in power electronics refers to: A. The process of converting DC to AC
B. The process of rapidly switching a semiconductor device
C. The process of changing the frequency of AC voltage
D. The process of converting AC to DC
Answer: B

35. A controlled rectifier is also known as: A. Inverter
B. Rectifier
C. Converter
D. Thyristor
Answer: D

36. Which of the following converters requires energy storage elements such as capacitors or inductors? A. Buck converter
B. Boost converter
C. Flyback converter
D. Diode rectifier
Answer: C

37. The primary advantage of using an H-bridge inverter is: A. Lower cost
B. Simplicity of control
C. Capability to generate both positive and negative output voltages
D. High efficiency
Answer: C

38. In a boost converter, the output voltage is: A. Always higher than the input voltage
B. Always lower than the input voltage
C. Sometimes higher and sometimes lower than the input voltage
D. Equal to the input voltage
Answer: A

39. The output of a PWM inverter typically has: A. High harmonic content
B. Low harmonic content
C. Pure sinusoidal waveform
D. None of the above
Answer: A

40. The purpose of a heat sink in power electronic devices is to: A. Increase the switching speed
B. Improve efficiency
C. Dissipate heat generated by the device
D. Provide electrical insulation
Answer: C

Power Electronics MCQs

More MCQS on Electronics MCQs

Leave a Comment Cancel reply