Power Electronics problems
- 1. A single phase half bridge inverter required to feed R-L loads needs
Options- A. 2 thyristors
- B. 4 thyristors
- C. 2 thyristors and two diodes
- D. 4 thyristors and 4 diodes Discuss
Correct Answer: 2 thyristors and two diodes
- 2. When a dc chopper feeds an RLE load, the load current, during steady state operation
Options- A. remains constant
- B. varies between maximum and minimum values
- C. may remain constant or vary
- D. is constant if R is constant Discuss
Correct Answer: varies between maximum and minimum values
- 3. In a single phase full wave ac regulator using two thyristors only, the gate circuits of the two thyristors
Options- A. must be isolated
- B. may or may not be isolated
- C. should be preferably, isolated
- D. should not be isolated Discuss
Correct Answer: must be isolated
- 4. Which of the following devices has metal-silicon junction?
Options- A. General purpose power diode
- B. Schottky diode
- C. SCR
- D. MOSFET Discuss
Correct Answer: Schottky diode
- 5. The main utility of SCR is due to
Options- A. gate triggering
- B. high temperature triggering
- C.
triggering - D. high breakdown voltage Discuss
Correct Answer: gate triggering
- 6. Assertion (A): A half wave controlled rectifier has poorer efficiency and higher ripple factor than a full wave controlled rectifier.
Reason (R): The use of a freewheeling diode in half wave controlled rectifier circuit improves the waveform of load current and circuit power factor.
Options- A. Both A and R are correct and R is correct explanation of A
- B. Both A and R correct but R is not correct explanation of A
- C. A is correct but R is wrong
- D. A is wrong but R is correct Discuss
Correct Answer: Both A and R correct but R is not correct explanation of A
- 7. A fully controlled bridge converter is feeding an RLE load. For some circuit conditions firing angle is 47°. If connections of battery are reversed, the firing angle is likely to be
Options- A. 47°
- B. less than 47°
- C. more than 47°
- D. either more or less than 47° Discuss
Correct Answer: more than 47°
- 8. The efficiency of a chopper circuit is about
Options- A. 80% or more
- B. around 50%
- C. around 20%
- D. around 5% Discuss
Correct Answer: 80% or more
- 9. Which of these devices can conduct in both directions?
Options- A. SCR
- B. SUS
- C. SBS
- D. UJT Discuss
Correct Answer: SBS
- 10. Mc Murray full bridge inverter uses
Options- A. 4 thyristors and 2 diodes
- B. 4 thyristors and 4 diodes
- C. 8 thyristors and 4 diodes
- D. 8 thyristors and 8 diodes Discuss
Correct Answer: 8 thyristors and 4 diodes
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