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  • Question
  • 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

  • Correct Answer
  • the output frequency can be even higher than the frequency of damped oscillations 


  • Power Electronics problems


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    • 1. 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
    • 2. 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
    • Discuss
    • 3. 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
    • Discuss
    • 4. 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
    • Discuss
    • 5. 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
    • Discuss
    • 6. 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
    • 7. A class B chopper operates in third quadrant.

    • Options
    • A. True
    • B. False
    • Discuss
    • 8. The duty cycle of a step down chopper is

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 9. 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.
    • Discuss
    • 10. 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


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