U21EE502 PED - UNIT 1

1. 1. How do you categories the converter and inverter grade SCR?

• a. Based on Turn On time

• b. Based on Turn off time

• c. Based on Commutation methods

• d. Power rating

2. 2.Which Power Semiconductor Device out of the following, is not a current controlled device?

• a. SCR

• b. TRIAC

• c. GTO

• d. MOSFET

3.The minimum duration of the pulse in a pulse triggering system for thyristors should be at -----------

• a.10 μs 3 sec

• b. 20 ms

• c. 10 ms

• d. 3 sec

4. 4.Which one of the following statement is true?

• A.MOSFET has a positive temperature coefficient whereas BJT has a negative temperature coefficient

• B.Both MOSFET and BJT have positive temperature coefficient

• C. Both MOSFET and BJT have negative temperature coefficient

• D.MOSFET has negative temperature coefficient whereas BJT has positive temperature coefficient

5.The conduction losses in IGBT is

• A. More than that of MOSFET  

• B. Lower than that of MOSFET

• C. Equal to that of MOSFET

• D. Equal to that of BJT

6. 6. In Class A and Class B commutation, the resonating circuit has to be

• A.Over Damped

• B. Critically Damped

• C. Under Damped

• D. Nagatively Damped

7. 7. For triggering of SCR used UJT, has the waveform

• A. Sine Wave

• B. Square Wave

• C. Sawtooth Wave

• D. Trapezoidal Wave

8. 8. 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.

9. 9. A freewheeling diode is connected across an inductive load is

• A.To restore conduction angle on phase

• B. To avoid negative reversal voltage drop

• C. To reduce the PRV

• D. All of the above

10. When a line commutated converter operates in the inverter mode

• A. It draws both real and reactive power from the AC supply

• B. It delivers both real and reactive power to the AC supply

• C. It delivers real power to the AC supply

• D. It draws reactive power from the AC supply