POWER ELECTRONICS MCQ PART 2
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POWER ELECTRONICS MCQ PART 2
Instructions: Click the answer button to see the correct answer.
1. Dynamic equalizing circuit is used for
- equal division of voltage across each thyristor in parallel.
- equal division of current through each thyristor in series.
- equal division of voltage across each thyristor.
- equal division of current through each thyristor in parallel.
Answer: c
2. 4 thyristors rated 200 V in series. The operating voltage of the string is 600 V. Derating factor of the string is
- 0.25.
- 0.75.
- 0.2.
- 0.7.
Answer: a
POWER ELECTRONICS MCQ PART 2
3. A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. Then calculate the value of n
- 70.
- 90.
- 80.
- 60.
Answer: c
4. For series connected SCR a dynamic equalising circuit consists of
- series R and diode with C across R.
- R and C in series but with diode across C.
- series R and diode with C across R.
- R and C in series but with diode across R
Answer: d
5. Anode current in an SCR consists of
- Both electron and holes.
- either electron or holes.
- electrons only.
- holes only.
Answer: a
POWER ELECTRONICS MCQ PART 2
6. Dynamic equalising circuit is useful
- to limit di / dt of SCR.
- both to limit dV / dt of SCR & for voltage equalisation
- to limit dV / dt of SCR.
- for voltage equalisation
Answer: b
7. Which following is a two terminal three layer device?
- None of these.
- MOSFET.
- BJT.
- Power dioed.
Answer: d
8. Which of following is not a power transistor?
- SITS.
- TRIAC.
- IGBTs.
- COOLMOS.
Answer: b
POWER ELECTRONICS MCQ PART 2
9. Which of following is normally ON device
- SIT.
- TRIAC.
- IGBT.
- BJT.
Answer: a
10. Power transistor are type of
- MOSFETs.
- BJTs.
- All of these
- IGBTs.
Answer: c
11. Which of the following is true?
- SIT is a high power, high voltage device.
- SIT is a low power, high frequency device.
- SIT is a high power, low frequency device.
- SIT is a high power, high frequency device.
Answer: d
POWER ELECTRONICS MCQ PART 2
12. A GTO can be turned on by applying
- Positive gate signal.
- Positive drain signal.
- None of these.
- Positive source signal.
Answer: a
13. SITH is also known as
- Filled controlled rectifier.
- Silicon controlled rectifier.
- Filled controlled diode.
- None of these.
Answer: c
14. The reverse recovery time of diode is trr = 3 sec and the rate off all of the diode current is di/dt = 30 A/Sec. The storage charge current QRR is
- 130 A
- 135 A
- 140 A
- 145 A
Answer: b
POWER ELECTRONICS MCQ PART 2
15. A power MOSFET has three terminals called
- Drain, source and base.
- Collector, emitter and base.
- Collector, emitter and gate.
- Drain, source and gate.
Answer: d
16. A modern power semiconductor device that combines the characteristic of BJT and MOSFET is
- GTO
- IGBT.
- FCT.
- MCT.
Answer: b
POWER ELECTRONICS MCQ PART 2
17. Thermal voltage VT can be given by
- KT/q.
- (K²/q)(T + 1/T – 1).
- qT/K.
- Kq/T.
Answer: a
18. IGBT combines the advantages of
- BJTs and SITs.
- SITs and MOSFETs.
- BJTs and MOSFETs.
- None of these.
Answer: c
POWER ELECTRONICS MCQ PART 2
19. COOLMOS device can be used in application up to power range of
- 100 KVA.
- 2 KVA.
- 500 VA.
- 1 KVA.
Answer: b
20. Compared to transistor, ______________ have lower on state conduction losses and higher power handling capability
- Thyristor
- Semi conductor diodes.
- MOSFETs.
- TRIACs.
Answer: a
POWER ELECTRONICS MCQ PART 2
21. A thyristor can termed as
- Square wave switch.
- AC switch.
- all of these
- DC switch.
Answer: d
21. Thyristor is nothing but a
- Amplifier with higher gain.
- Amplifier with large current gain.
- Controlled switch.
- Controlled transistor.
Answer: c
22. BCT is used for
- High power current control.
- Low power current control.
- High power phase control.
- Low power phase control.
Answer: c
POWER ELECTRONICS MCQ PART 2
23. Which of following devices has highest di/dt and dv/dt capability?
- SITH.
- SIT.
- SCR.
- GTO.
Answer: d
24. Which of the following is disadvantage of fast recovery diodes?
- Doping is carried out.
- Recovery is only 50 µs.
- Recovery is only 5 µs.
- None of these.
Answer: a
25. A power semiconductor may undergo damage due to
- High dv/dt.
- High di/dt.
- Low dv/dt.
- Low di/dt.
Answer: b
26. If the anode current is 800 A, then the amount of current required to turn off the GTO is about
- 400 A.
- 600 A.
- 200 A.
- 20 A.
Answer: c
POWER ELECTRONICS MCQ PART 2
27. Which semiconductor device acts like a diode and two transistor?
- SCR.
- UJT.
- Triac.
- Diac.
Answer: c
28. The latching current of GTO should be of order
- 500 mA.
- 2 A.
- 100 mA.
- 1 A.
Answer: b
29. The maximum di/dt in a SCR is
- Directly proportional to supply voltage.
- none of these
- Directly proportional to inductance in the circuit.
- both
Answer: d
POWER ELECTRONICS MCQ PART 2
30 Switching frequency of SITH is
- 60 KHz.
- Practical way of obtaining static voltage equalization in series connected SCRs is by the use of
- 5 KHz.
- 10 KHz.
- 100 KHz.
Answer: f
31. A single phase full bridge inverter can operate in load commutation mode in case load consists of
- RLC overdamped.
- RLC critically damped.
- RL.
- RLC underdamped.
Answer: a
32. The function of snubber circuit connected across the SCR is to
- suppress dV / dt.
- decrease di / dt.
- increase dV / dt.
- decrease dV / dt.
Answer: a
POWER ELECTRONICS MCQ PART 2
33. An SCR is considered to be semi controlled device because
- it can be turned OFF but not ON with a gate pulse
- it can be turned ON only during one half cycle of an AC
- it conducts only during one half cycle of an alternating current wave
- it can be turned ON but not OFF with a gate pulse
Answer: b