# Power Electronics 6

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Power Electronics 6

Part 6: List for questions and answers of Power Electronics

Q1. Which of following devices has highest di/dt and dv/dt capability?

a) SIT

b) SITH

c) GTO

d) SCR

Q2. Which of the following is disadvantage of fast recovery diodes?

a) Recovery is only 5 Us

b) Recovery is only 50 Us

c) Doping is carried out

d) None of these

Q3. A power semiconductor may undergo damage due to?

a) High di/dt

b) Low di/dt

c) High dv/dt

d) Low dv/dt

Q4. If the anode current is 800 A, then the amount of current required to turn off the GTO is about?

a) 20 A

b) 600 A

c) 400 A

d) 200 A

Q5. Which semiconductor device acts like a diode and two transistor?

a) UJT

b) Diac

c) Triac

d) SCR

Q6. The latching current of GTO should be of order?

a) 100 mA

b) 500 mA

c) 1 A

d) 2 A

Q7. The maximum di/dt in a SCR is?

a) Directly proportional to supply voltage

b) Directly proportional to inductance in the circuit

c) Inversely proportional to supply voltage

d) Both A and B

Q8. Switching frequency of SITH is?

a) 5 KHz

b) 10 KHz

c) 60 KHz

d) 100 KHz

Q9. Practical way of obtaining static voltage equalization in series connected SCRs is by the use of?

a) one resistor across the string

b) resistors of different values across each SCR

c) resistors of the same value across each SCR

d) one resistor in series with each SCR

Q10. A single phase full bridge inverter can operate in load commutation mode in case load consists of?

a) RL

b) RLC underdamped

c) RLC overdamped

d) RLC critically damped

Q11. The function of snubber circuit connected across the SCR is to?

a) suppress dV/dt

b) increase dV/dt

c) decrease dV/dt

d) decrease di/dt

Q12. The power demand can be estimated approximately by ?

b) Mathematical method

c) Statistical method

d) Economic parameters

Q13. What is the advantage of HRC fuses over Rewirable fuses?

a) High speed operation

b) High rupturing capacity

c) No ageing effect

d) All of the above

Q14. If a shunt motor is started with its field winding open then?

a) It will rotate at the same speed as that with its field winding closed

b) It will rotate at less speed as that with its field winding closed

c) It will rotate at dangerously high speed

d) None of these

Q15. Electrical power output in a d.c. generator is equal to?

a) Electrical power developed in armature – copper losses

b) Mechanical power input-iron and friction losses

c) Electrical power developed in armature – iron and copper losses

d) Mechanical power input-iron and friction losses – copper losses

Q16. AC power in a load can be controlled by using?

a) Two SCR’s in parallel opposition

b) Two SCR’s in series

c) Three SCR’s in series

d) Four SCR’s in series

Q17. An SCR is made up of silicon because?

a) Silicon has large leakage current than germanium

b) Silicon has small leakage current than germanium

c) Silicon has small leakage voltage than germanium

d) Silicon has large leakage voltage than germanium

Q18. The output power of the cascaded amplifier / attenuator system can be determined using ?

a) Actual gain of amplifier

b) Actual gain of amplifier and attenuator

c) Gain in dB of amplifier and attenuator

d) Actual gain of attenuator

Q19. LISN is a device used to measure conducted emissions. LISN stands for?

a) Line integrated stabilization network

b) Line impedance stabilization network

c) Line integrated stored network

d) Laser integrated stabilization networking

Q20. What is the advantage of HRC fuses over Rewirable fuses?

a) High speed operation

b) High rupturing capacity

c) No ageing effect

d) All of the above

Part 6: List for questions and answers of Power Electronics