To turn off an SCR, it is necessary to reduce its current to less than : trigger

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Question
To turn off an SCR, it is necessary to reduce its current to less than :
Options
A. trigger current
B. holding current
C. breakover current
D. none of the above

Correct Answer

holding current

Power Electronics problems

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1. An ideal rectifier should have
Options
A. 100% efficiency, zero ripple factor, zero harmonic factor and unity displacement factor
B. 100% efficiency, zero tipple factor, zero harmonic factor and zero displacement factor
C. 100% efficiency, zero ripple factor, unity harmonic factor and unity displacement factor
D. 100% efficiency, unity ripple factor, zero harmonic factor and unity displacement factor

3. In a modified series inverter with two inductors and two capacitors, the load current
Options
A. has 2 parallel paths
B. has only one parallel path
C. can have three parallel paths
D. has four parallel paths

4. In a bridge inverter
Options
A. an output transformer is essential
B. an output transformer is not essential
C. an output transformer cannot be connected
D. an output transformer, if used, can improve the efficiency of the circuit

6. Assertion (A): The circuit of figure thyristor will conduct for 180� during positive half cycle if it is continuously fired.

Reason (R): A thyristor can conduct only when it is forward biased.
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

7. The effect of source inductance in a 3 phase fully controlled bridge converter is to
Options
A. decrease the output voltage
B. increase the output voltage
C. decrease the output voltage and increase the output current
D. increase the output voltage and decrease the output current

8. Class A and class B chopper
Options
A. operate in first quadrant
B. operate in second quadrant
C. class A chopper operates in first quadrant while class B operates in second quadrant
D. may operate in either first or second quadrant

9. In a modified series inverter
Options
A. the maximum output frequency is less than frequency of damped oscillations
B. the output frequency can be even higher than the frequency of damped oscillations
C. the output frequency cannot exceed the frequency of damped oscillations
D. any of the above

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