Electrical Engineering MCQ Question Papers: Campus Placement
Subject: Power Electronics 4
Part 4: List for questions and answers of Power Electronics
Q1. Materials used in heat sink should have?
a) High thermal conductivity
b) Large surface area
c) High melting point
d) All of these
Q2. What is used to protect a thyristor from high di / dt conditions?
a) Fuse
b) Snubber circuit
c) Inductor
d) Voltage clamping device
Q3. Which of the following is used in SCR to protect from high dV / dt?
a) Snubber circuit
b) Fuse
c) Equalizing circuit
d) Circuit breaker
Q4. What happen due to high di / dt?
a) Breakdown of junction
b) Local hot spot
c) Insulation failure
d) None of these
Q5. What may happen high dV / dt?
a) Unwanted turn ON
b) Breakdown of J2 junction
c) Both A and B
d) Anyone of these
Q6. Why resistor is used in Snubber circuit ?
a) To minimize the loss
b) To minimize the charging current
c) To minimize the discharging current
d) All of these
Q7. Snubber circuit is used with SCR?
a) In series
b) In parallel
c) Either series or parallel
d) Anti parallel
Q8. Delay time is defined by the interval when?
a) Gate current increases from 90 % to 100 % of its final value
b) Anode current reaches 10 % from forward leakage current
c) Anode voltage drops from 100 % to 90 % of its actual valuev
d) All of these
Q9. Rise time is defined by the interval when?
a) Gate current rises from 90 % to 100 % of it final value
b) Anode voltage drops from 90 % to 10 % of its initial value
c) Anode current rises 10 % to 90 % of its final value
d) Both B and C
Q10. Spread time is defined as the interval during which?
a) Anode voltage drops from 10 % of its initial value to zero
b) Anode current rises from 90 % to its final value
c) Both (A) and (B)
d) Anode current rises from 10 % to 90 % of its final value
Q11. Maximum power loss occurs during?
a) Delay time
b) Rise time
c) Spread time
d) All
Q12. The typical time of rising time lies between?
a) 10 – 20 us
b) 40 – 60 us
c) 1 – 4 us
d) 90 – 100 us
Q13. During which time maximum conduction spreading take place in the thyristor during turn ON?
a) Delay time
b) Spread time
c) Rise time
d) Same for every case
Q14. Typical range of thyristor turn OFF time is?
a) 3 – 10 us
b) 3 – 50 us
c) 3 – 100 us
d) 3 – 500 us
Q15. ON state voltage drop across SCR lie between the range?
a) 0 – 0.5 V
b) 0.5 – 1 V
c) 1 – 1.5 V
d) 1.5 – 2 V
Q16. SCRs are used in series to meet?
a) High current demand
b) Low voltage demand
c) Low current demand
d) High voltage demand
Q17. To meet high current demand we use SCRs in?
a) Series connection
b) Parallel connection
c) Anti parallel connection
d) Both B and C
Q18. By which one of the following we can measure the reliability of a string?
a) String efficient
b) Reliability factor
c) Factor of safety
d) Derating factor
Q19. Dynamic equalizing circuit is used for?
a) Equal division of voltage across each thyristor
b) Equal division of current through each thyristor in parallel
c) Equal division of voltage across each thyristor in parallel
d) Equal division of current through each thyristor in series
Q20. 4 thyristors rated 200 V in series. The operating voltage of the string is 0.600 V. Derating factor of the string is?
a) 0.75
b) 0.7
c) 0.2
d) 0.25
Part 4: List for questions and answers of Power Electronics
Q1. Answer: d
Q2. Answer: c
Q3. Answer: a
Q4. Answer: b
Q5. Answer: c
Q6. Answer: c
Q7. Answer: b
Q8. Answer: d
Q9. Answer: d
Q10. Answer: b
Q11. Answer: b
Q12. Answer: c
Q13. Answer: b
Q14. Answer: c
Q15. Answer: c
Q16. Answer: d
Q17. Answer: b
Q18. Answer: d
Q19. Answer: a
Q20. Answer: d