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  • Question
  • When an SCR is reverse biased


  • Options
  • A. two junctions are reverse biased and one junction is forward biased.
  • B. all the three junctions are reverse biased.
  • C. one junction is reverse biased and two junctions are forward biased.
  • D. any of the above depending on the magnitude of reverse bias.

  • Correct Answer
  • two junctions are reverse biased and one junction is forward biased. 


  • Power Electronics problems


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    • 1. The duty cycle of a step down chopper is

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 2. A class B chopper operates in third quadrant.

    • Options
    • A. True
    • B. False
    • Discuss
    • 3. A single phase cycloconverter with centre tapped input transformer requires

    • Options
    • A. 2 thyristors
    • B. 4 thyristors
    • C. 8 thyristors
    • D. either 2 or 4 thyristors
    • Discuss
    • 4. 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
    • Discuss
    • 5. 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
    • Discuss
    • 6. From which instant is the turn off time of a thyristor defined

    • Options
    • A. when anode voltage becomes zero
    • B. when anode current becomes zero
    • C. when both anode voltage and current become zero
    • D. none of the above
    • Discuss
    • 7. The number of thyristors in a single phase fully controlled bridge rectifier is

    • Options
    • A. 16
    • B. 8
    • C. 4
    • D. 2
    • Discuss
    • 8. In a 3 phase bridge inverter with 120° mode of operation the. number of thyristors conducting at one time are

    • Options
    • A. 1
    • B. 2
    • C. 3
    • D. 4
    • Discuss
    • 9. The snubber circuit consists of

    • Options
    • A. a capacitor connected in series with thyristor
    • B. a capacitor connected in parallel with thyristor
    • C. a resistor and capacitor in series connected across thyristor
    • D. none of the above
    • Discuss
    • 10. In a dual converter operated in circulating current mode, the circulating current flows

    • Options
    • A. when load current is zero
    • B. when load current is non-zero
    • C. even when load current is zero
    • D. none of the above
    • Discuss


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