Power Electronics problems
- 1. In a stud mounted SCR, the stud is
Options- A. in thermal contact with heat sink
- B. insulated from heat sink
- C. in electrical and thermal contact with heat sink
- D. in either electrical or thermal contact with heat sink Discuss
Correct Answer: in electrical and thermal contact with heat sink
- 2. McMurray Bedford full bridge inverter uses
Options- A. natural commutation
- B. auxiliary commutation
- C. complementary commutation
- D. any of the above Discuss
Correct Answer: complementary commutation
- 3. In a single phase full wave regulator feeding an R-L load, the power factor angle of load is ?. The range of control of firing angle a is
Options- A. 0 ? a ? p
- B. ? ? a ? p
- C. 0 ? a ? (p - ?)
- D. ? ? a ? (p + ?) Discuss
Correct Answer: ? ? a ? p
- 4. If a step down chopper is fed by a dc voltage V with Ton and Toff are on and off periods then
is
Options- A. average output voltage
- B. rms output voltage
- C. average or rms output voltage depending on load
- D. neither of the above Discuss
Correct Answer: average output voltage
- 5. In a thyristor the gate lead is connected to the n layer near the p layer to which anode is connected.
Options- A. True
- B. False Discuss
Correct Answer: False
- 6. The characteristics of which device has peak point and valley point
Options- A. SCR
- B. PUT
- C. SCS
- D. Shockley diode Discuss
Correct Answer: PUT
- 7. The two-transistor model of a thyristor consists of two transistors :
Options- A. one n-p-n and other p-n-p
- B. both p-n-p
- C. both n-p-n
- D. one n-p-n and other UJT Discuss
Correct Answer: one n-p-n and other p-n-p
- 8. Which of these commutation methods uses an external pulse for commutation?
Options- A. Class A
- B. Class C
- C. Class E
- D. Class F Discuss
Correct Answer: Class E
- 9. In a half bridge inverter each thyristor is gated at a frequency f. The output frequency is
Options- A. 2 f
- B. f
- C. 0.5 f
- D. 0.25 f Discuss
Correct Answer: f
- 10. Assertion (A): The turn on time of SCR is about 1 to 4 ms.
Reason (R): The turn off time of SCR is about 10 to 300 ms.
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
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