Discussion
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- Question
Two single phase semi-converters are connected in series to form a series converter. The input is v = Vm sin ?t and a1, a2 are the firing angles. If a1 = 0, the dc output voltage is
Options- A.
(1 + cos a2) - B. (2 + cos a2)
- C. (3 + cos a2)
- D. (4 + cos a2)
- Correct Answer
- (3 + cos a2)
- 1. When a UJT is used as a relaxation oscillator the current should be
Options- A. less than Ip
- B. more than Iv
- C. more than Ip but less than Iv
- D. negative Discuss
- 2. In a series inverter
Options- A. the commutating elements carry full load current
- B. the commutating elements carry upto 50% of load current
- C. the commutating elements do not carry load current
- D. any of the above Discuss
- 3. For an illumination control circuit it is advisable to use a matched TRIAC-DIAC pair.
Options- A. True
- B. False Discuss
- 4. Which chopper circuit uses saturable reactor?
Options- A. Auxiliary commutated
- B. Jones chopper
- C. Morgan chopper
- D. Load commutated Discuss
- 5. A single phase semiconverter is supplying RLE load and has a freewheeling diode across the load. The firing angle is a. The freewheeling diode conducts for
Options- A. a° in each half cycle
- B. (p - a)° in each cycle
- C. a° in one full cycle
- D. (p + a)° in each half cycle Discuss
- 6. If we connect two silicon unilateral switches in anti- parallel we get
Options- A. SCR
- B. SBS
- C. SCS
- D. UJT Discuss
- 7. When UJT is used for thyristor gate signal, the output of UJT is
Options- A. sine wave
- B. square wave
- C. saw tooth wave
- D. either (a) or (c) Discuss
- 8. In a single phase full wave regulator feeding a resistive load, the average current over one full cycle
Options- A. is always zero
- B. cannot be zero
- C. may be sometimes zero
- D. is always positive Discuss
- 9. A UJT exhibits negative resistance characteristics when
Options- A. Current is less than valley current
- B. Current is less than peak current
- C. Current is more than peak current but less than valley current
- D. None of the above Discuss
- 10. A 3 phase induction motor is controlled by voltage and frequency control such that the ratio V/f is constant. At 50 Hz, the starting torque is 100 N-m. At 25 Hz, the starting torque
Options- A. will be less than 100 N-m
- B. will be more than 100 N-m
- C. may be more or less than 100 N-m depending on motor parameters
- D. very small Discuss
Power Electronics problems
Search Results
Correct Answer: more than Ip but less than Iv
Correct Answer: the commutating elements carry full load current
Correct Answer: True
Correct Answer: Morgan chopper
Correct Answer: a° in each half cycle
Correct Answer: SBS
Correct Answer: saw tooth wave
Correct Answer: is always zero
Correct Answer: Current is more than peak current but less than valley current
Correct Answer: will be more than 100 N-m
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