Power Electronics problems
- 1. On load tap changer using thyristors can have a maximum of two taps.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Any number of taps are possible.
- 2. In controlled heating circuits, thyristors act as
Options- A. rectifier
- B. inverter
- C. ac regulator
- D. chopper Discuss
Correct Answer: ac regulator
Explanation:
The output voltage is controlled ac.
- 3. A single phase full converter gives maximum and minimum output voltage at firing angles of
Options- A. 0 and 180° respectively
- B. 180° and 0° respectively
- C. 0 and 90° respectively
- D. 90° and 0° respectively Discuss
Correct Answer: 0 and 180° respectively
Explanation:
Output voltage is maximum if a = 0 and is minimum if a = 180°.
- 4. A Shockley diode can be used
Options- A. in place of SCR
- B. as a trigger switch for SCR
- C. in place of UJT
- D. both in place of SCR and as a trigger switch for SCR Discuss
Correct Answer: as a trigger switch for SCR
Explanation:
It is a four layered PNPN device without a gate terminal. Its characteristics is similar to that of SCR with zero gate current. It is acting as a trigger switch for Thyristor.
- 5. As regards single phase dual converter
Options- A. the change in operation from one quadrant to the other is faster in non-circulating current mode
- B. the change in operation from one quadrant to the other is faster in circulating current mode
- C. the time response to change in operation from one quadrant to other is the same in both the modes
- D. the time response to change in operation from one quadrant to the other may be faster in any of the two modes Discuss
Correct Answer: the change in operation from one quadrant to the other is faster in circulating current mode
- 6. In a parallel inverter
Options- A. the commutating capacitor C is across the primary of transformer and the load is across the secondary
- B. the commutating capacitor and load are connected across the secondary of transformer
- C. the commutating capacitor C and load are connected in series and the combination is across the secondary of transformer
- D. none of the above Discuss
Correct Answer: the commutating capacitor C is across the primary of transformer and the load is across the secondary
- 7. In a fully controlled bridge converter feeding a resistive load the waveshapes of output voltage and output current
Options- A. are always similar
- B. can never be similar
- C. may be similar or dissimilar
- D. are similar only if a = 0 Discuss
Correct Answer: are always similar
Explanation:
For resistive load output current is always proportional to output voltage.
- 8. Assertion (A): Snubber circuit has an RC series circuit in parallel with SCR
Reason (R): Voltage across a capacitor can not change instantaneously.
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 are correct and R is correct explanation of A
Explanation:
Since voltage across capacitor cannot change instantaneously it protects SCR against high 
.
.
- 9. Which of these commutation methods is used in AC-DC converters?
Options- A. Class A
- B. Class C
- C. Class D
- D. Class F Discuss
Correct Answer: Class F
Explanation:
Class F is natural commutation AC = DC converter use natural (or line) commutation.
- 10. A silicon controlled switch has :
Options- A. 2 leads
- B. 3 leads
- C. 4 leads
- D. 5 leads Discuss
Correct Answer: 4 leads
Explanation:
Anode, cathode, anode gate and cathode gate.
More in Electronics and Communication Engineering:
Programming
Copyright ©CuriousTab. All rights reserved.