Power Electronics and Drives MCQ-3

1. Electric Derive is becoming more and more popular because

(A) It is simple and reliable
(B) It is cheaper in cost
(C) It provides smooth and easy control
(D) All of the above

2. Which converter (s) can be used for D.C. series motor control-

(A) Semi-converters
(B) Half-wave converters
(C) Full-converters
(D) Semi-converters and Full-converters

3. Application of cyclo converters include

(A) Speed control of A.C. Drives
(B) Static VAR compensation
(C) Induction heating
(D) All of the above

4. In Induction heating, which of the following is abnormally high?

(A) Phase Angle
(B) Frequency
(C) Current
(D) Voltage

5. Over Charging of the battery results in –

(A) High temp, Corrosion of plates, Oxidation of scparators, loss of water
(B) Irreversible sulphation, reversal of cells loss of capacity
(C) Battery is in good condition
(D) All of the above

6. A Thyristor is a

(A) P-N-P device
(B) N-P-N device
(C) P-N-P-N device
(D) P-N device

7. The static V-I curve for the Thyristor is plotted for

(A) Anode current vs gate current for different values of Anode-cathode voltage
(B) Anode current vs Anode-cathode voltage for different values of gate current
(C) Anode cathode voltage vs gate current for different values of Anode current
(D) Gate current vs Gate voltage for different values of Anode current

8. For the Thyristor to remain in the conducting(ON) state

(A) Gate signal is continuously required
(B) No continuous gate signal is required
(C) No forward Anode-cathode voltage is required
(D) Negative gate signal is continuously required

9. The forward dv/dt rating of an SCR

(A) Increase with increase in Junction temp.
(B) Decrease with increase in Junction temp.
(C) Increase with decrease in RMS value of forward Anode-cathode voltage
(D) Decrease with decrease in RMS value of forward Anode-cathode voltage

10. In a single phase Half-wave circuit with load RL and a free-wheeling Diode, the load voltage during free-wheeling period will be

(A) Zero
(B) Positive
(C) Negative
(D) Positive then Negative

11. A single phase full controlled bridge converter uses

(A) 4 SCRs and 2 Diodes
(B) 4 SCRs
(C) 6 SCRs
(D) 2 SCRs and 4 Diodes

12. A three-phase three-pulse, M-3 type controlled converter uses number of SCRs

(A) One
(B) Two
(C) Three
(D) Frour

13. A cycloconverter is a :

(A) Frequency changer from higher to lower frequency with one-stage conversion
(B) Frequency changer from lower to higher with one-stage converison
(C) Both (a) and (b)
(D) Neither (a) Nor (b)

14. A chopper may be thought as a :

(A) inverter with DC input
(B) DC equivalent of an AC Transformer
(C) Diode Rectifier
(D) DC equivalent of an Inducton Motor

15. In Type C chopper, if only one switch is operated –

(A) Only one quadrant operation will be obtained
(B) Two quadrant operation will be obtained
(C) The chopper will not work
(D) None of the above

16. In constant frequency system of chopper ________ is varied

(A) Vs
(B) Ton
(C) T
(D) f

17. In voltage fed Thyristor inverters ________ commutation is required.

(A) Load
(B) Forced
(C) Self
(D) Any of the above

18. In the single-pulse width modulation method the output voltage wave form is symmetrical about-

(A) π
(B) 2π
(C) π/2
(D) π/4

19. Line-commutated inverters have

(A) A.C. on the supply side and DC on the load side
(B) A.C. on both supply and load side
(C) D.C. on both supply and load side
(D) D.C. on the supply side and A.C. on the load side

20. The series-inverter control method is an

(A) Internal voltage control method
(B) External voltage control method
(C) External frequency control method
(D) None of the above