Power Electronics problems
- 1. In the circuit of figure, the load current when thyristor is off
Options- A. is constant
- B. increases exponentially
- C. decreases exponentially
- D. zero Discuss
Correct Answer: decreases exponentially
- 2. Thyristors connected in series need :
Options- A. static equalizing circuit
- B. dynamic equalizing circuit
- C. both static and dynamic equalizing circuits
- D. none of the above Discuss
Correct Answer: both static and dynamic equalizing circuits
- 3. A single phase bridge type cycloconverter uses eight thyristors.
Options- A. True
- B. False Discuss
Correct Answer: True
- 4. A single phase full converter can operate in
Options- A. 4 quadrants
- B. 3 quadrants
- C. 2 quadrants
- D. 1 quadrant Discuss
Correct Answer: 2 quadrants
- 5. In a thyristor, the forward breakover voltage
Options- A. is constant
- B. may be constant or may depend on gate current
- C. decreases as gate current is increased
- D. increases as gate current is increased Discuss
Correct Answer: decreases as gate current is increased
- 6. A single phase half wave converter is feeding a resistive load. Output dc power is Pdc and total power delivered to load is Pac then
Options- A. Pdc = Pac for all values of firing angles
- B. Pdc = Pac if firing angle is less than 180°
- C. Pdc < Pac for all values of firing angles
- D. Pdc < Pac if firing angle is less than 180° Discuss
Correct Answer: Pdc < Pac if firing angle is less than 180°
- 7. A relaxation oscillator uses
Options- A. tunnel diode
- B. UJT
- C. both tunnel diode and UJT
- D. PIN diode Discuss
Correct Answer: UJT
- 8. In a 3 phase semiconverter, the freewheeling diode comes into operation only if firing angle
Options- A. is zero
- B. is 60°
- C. is more than 60°
- D. is more than 90° Discuss
Correct Answer: is more than 60°
- 9. A current source inverter has simple commutation circuit.
Options- A. True
- B. False Discuss
Correct Answer: True
- 10. In a full bridge inverter, the waveshape of load current depends on
Options- A. relative values of load parameters R, L and C
- B. relative values of load parameters R and L
- C. relative values of load parameters L and C
- D. gating frequency Discuss
Correct Answer: relative values of load parameters R, L and C
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