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Power Electronics problems

1. A semiconverter feeding an RLE load operates in
Options
A. first quadrant only
B. first and second quadrants
C. first and fourth quadrants
D. first and third quadrants

2. Assertion (A): Inverters and choppers use fast switching thyristors
Reason (R): Fast switching SCR has low turn off time.
Options
A. Both A and R are correct and R is correct explanation of A
B. Both A and R correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

4. The terminals of a power BJT are called
Options
A. emitter, base, collector
B. emitter, base, drain
C. source, base, drain
D. source, base, collector

5. In a single phase full wave converter (M - 2 connection) feeding a highly inductive load, the firing angle for each thyristor is a in the respective half cycle. The period of conduction of each thyristor is
Options
A. p - a
B. p
C. p + a
D. p - 2a

7. Figure shows a chopper feeding RLE load, The free wheeling diode conducts when
Options
A. thyristor is on
B. thyristor is off
C. both when thyristor is on and thyristor is off
D. partly when thyristor is off and partly when thyristor is on

8. A chopper
Options
A. converts constant voltage dc into ac and then into variable voltage dc
B. converts constant voltage dc into variable voltage dc directly
C. converts ac of one frequency into ac of another frequency
D. converts ac to dc

9. Assertion (A): If the duty cycle of chopper is low the current would not become discontinuous
Reason (R): If the time constant L/R of the load in chopper is low the current may become discontinuous.
Options
A. Both A and R are correct and R is correct explanation of A
B. Both A and R correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

10. In a thyristor the gate current is increased, then
Options
A. anode current will increase
B. anode current will decrease
C. anode current will remain constant
D. anode current may increase or decrease

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