Discussion
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- Question
The application of gate signal decreases the break over voltage of on SCR.
Options- A. True
- B. False
- Correct Answer
- True
- 1. A fully controlled bridge converter feeds a highly inductive load such that the load current can be assumed to be constant. The wave shape of input current is
Options- A. dc
- B. sinusoidal
- C. rectangular
- D. none of the above Discuss
- 2. Modified 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
- 3. The power factor at the input terminals of a cyclo- converter is generally
Options- A. low and leading
- B. low and lagging
- C. high and leading
- D. high and lagging Discuss
- 4. A dc series motor is coupled to a load whose torque is proportional to speed. It is fed by a single phase ac supply through a full converter. When speed is 500 rpm, firing angle is 45°. It is desired to raise the speed. It will be necessary to
Options- A. decrease the firing angle
- B. increase the firing angle
- C. either decrease or increase the firing angle depending on the required speed
- D. decrease the load torque Discuss
- 5. Assertion (A): Thyristors can be used in controlled heating, excitation systems of alternators, speed control of motors and HVDC
Reason (R): A static var system using thyristors is very commonly used in high voltage ac systems.
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
- 6. Ripple factor RF and form factor FF are related as
Options- A. RF = FF2 - 1
- B. RF = (FF2 - 1)0.5
- C. RF = FF - 1
- D. RF = (FF - 1)0.5 Discuss
- 7. In integral cycle control of ac regulator, the input power factor is equal to
Options- A. duty cycle a
- B. a2
- C. a
- D. (a)1/3 Discuss
- 8. A single phase fully controlled bridge converter is feeding an RLE load. Input voltage is Vm sin ?t and firing angle is a. If average current is I0, then
Options- A.
cos a = RI0 + E - B.
cos a = RE0 + E - C. cos a = E0 - RI0
- D. cos a = E - RI0
Discuss
- 9. In a 3 phase semiconverter, the output voltage becomes discontinuous for
Options- A. firing angle > 30°
- B. firing angle > 60°
- C. firing angle > 90°
- D. firing angle > 120° Discuss
- 10. A static excitation system uses
Options- A. transformer and thyristors
- B. transformer and ac exciter
- C. dc exciter and ac exciter
- D. transformer and dc exciter Discuss
Power Electronics problems
Search Results
Correct Answer: rectangular
Correct Answer: 8 thyristors and 8 diodes
Correct Answer: low and lagging
Correct Answer: decrease the firing angle
Correct Answer: Both A and R correct but R is not correct explanation of A
Correct Answer: RF = (FF2 - 1)0.5
Correct Answer: a
Correct Answer:
cos a = RI0 + E Correct Answer: firing angle > 60°
Correct Answer: transformer and thyristors
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