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- Question
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
- Correct Answer
- Both A and R are correct and R is correct explanation of A
ExplanationSince voltage across capacitor cannot change instantaneously it protects SCR against high
.
Power Electronics problems
Search Results
- 1. 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.- 2. 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
- 3. 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
- 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. 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°.- 6. 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.- 7. 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.- 8. The number of gates in an SCR is
Options- A. 1
- B. 3
- C. 4
- D. 6 Discuss
Correct Answer: 1
- 9. Assertion (A): A high dv/dt may cause triggering of a thyristor.
Reason (R): A high dv/dt results in charging current in the thyristor.
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:
The charging current may cause triggering.- 10. A thyristor has maximum allowable junction temperature of 110° C and the ambient temperature is 40°C, If the maximum internal power dissipation is 50 W, the thermal resistance is
Options- A. 2° C/W
- B. 1.4° C/W
- C. 0.7°C/W
- D. 2.2° C/W Discuss
Correct Answer: 1.4° C/W
Explanation:
.
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