Power Electronics Multiple Choice Questions

Electronics and Communication Multiple Choice Questions

1. A step up chopper is required to deliver a load voltage of 660V from a DC source of 220V. Let the non-conduction time of thyristor be 100 micros required the requited pulse width, ton:

a. 150 micro sec

b. 200 micro sec

c. 330 micro sec

d. 240 micro sec

2. The thyristor can be turned on by applying?

a. a positive signal to gate

b. a negative signal to gate

c. holding current to the gate

d. none of the above

3. When two SCRs are connected in parallel configuration?

a. the SCR with lower dynamic resistance will carry lesser value of current

b. the SCR with lower dynamic resistance will carry higher value of current

c. both the SCR with carry equal values of current even if their dynamic resistance are different

d. none of the above

4. A class-C chopper (DC to DC converter) is also known as?

a. one-quadrant regulator

b. two-quadrant chopper

c. steady state chopper

d. all of the above

5. The flyback converter topology in a DC to DC switched mode power supply?

a. should be restricted to low power application

b. can be used for high power application

c. would be selected depending upon the DC load of the equipment in question

d. can be selected without considerations of power requirement of the equipment in questions.

6. A UPS is an example of?

a. a DC SMPS

b. an AC SMPS

c. a DC to DC converter

d. a voltage regulation device

7. An n-channel enhancement MOSFET?

a. has a physical channel

b. has no physical channel

c. is similar in construction to a p channel depletion MOSFET

d. none of these

8. The enhancement MOSFETs responds to?

a. positive and negative gate voltages

b. positive gate voltage only

c. negative voltage only

d. none of above is true

9. A DC chopper (DC to DC converter) is turned on for 30 micro sec and turned off for 10 micro sec. What is its duty cycle?

a. 0.62

b. 0.92

c. 0.75

d. 0.85

10. In a three-phase bridge inverter?

a. firing of SCRs can be done for a period of 120 degree only

b. firing of SCRs can be done for a period of 180 degree only

c. firing of SCRs can be done for a period of 120 degree and 180 degree periods

d.  none of the above

Answers:

1.  b

2. a

3. b

4. b

5. a

6. b

7. b

8. b

9. c

10. c

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