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Power Electronics problems

1. A single phase half wave rectifier is feeding a resistive load. Input voltage v = V_m sin ?t. The output dc voltage is V_dc and output rms voltage is V_rms . If firing angle is 180�, V_dc and V_rms respectively are
Options
A. 0 and 0
B.
C. 0 and - V_m
D.

2. Assertion (A): A TRIAC is a bidirectional SCR.
Reason (R): A TRIAC is a four layers 3 terminal device and can conduct in both directions.
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

3. In the below figure the average load current is 15 A. The rms value of transformer secondary current is
Options
A. 15 A
B. 10.61 A
C. 7.5 A
D. 14.14 A

4. In a circuit using a full wave converter (M - 2 connection) the PIV of each thyristor is 400 V. For the same output voltage and fully controlled bridge converter, PIV will be
Options
A. 400 V
B. 800 V
C. 200 V
D. 2002 V

5. If V_dc1 is the dc output voltage in half wave controlled rectifier circuit feeding resistive load and V_dc2 is the dc output voltage in full wave controlled rectifier circuit (M - 2 connection) feeding resistive load, then
Options
A. V_dc1 = 0.5 V_dc2 for all values of firing angle
B. V_dc1 = V_dc2 for all values of firing angle
C. V_dc1 ? 0.5 V_dc2 for all values of firing angle
D. V_dc1 ? 0.5 V_dc2 for all values of firing angle

6. The total number of leads in reverse conducting thyristor is
Options
A. 2
B. 3
C. 1
D. 4

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7. Current derating may be necessary when thyristors are operating in
Options
A. series
B. parallel
C. series or parallel
D. none of the above

8. Assertion (A): A transistor requires a continuous base signal for conduction but a thyristor requires a gate pulse.
Reason (R): Transistor find widespread application in power electronic circuits.
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

9. The phenomenon of overlap in converter operation due to
Options
A. source resistance
B. source inductance
C. both source resistance and source inductance
D. high value of firing angle

10. A single phase semiconverter is feeding a highly inductive load and has freewheeling diode across the load. The waveshapes of output voltage and output current
Options
A. are similar
B. are not similar
C. may be similar or dissimilar
D. are similar only if firing angle is zero

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