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  • Question
  • 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

  • Correct Answer
  • A is correct but R is wrong 

    Explanation
    If duty cycle is low, current may become discontinuous.

    Power Electronics problems


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    • 1. 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
    • Discuss
    • 2. 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
    • Discuss
    • 3. A semi converter operates in two quadrants.

    • Options
    • A. True
    • B. False
    • Discuss
    • 4. 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
    • Discuss
    • 5. 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
    • Discuss
    • 6. 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
    • Discuss
    • 7. Assertion (A): An ideal rectifier should have unity harmonic factor

      Reason (R): An ideal rectifier should have unity displacement factor.


    • 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
    • 8. A thyristor has a maximum allowable junction temperature of 120°C and the ambient temperature is 40°C. If thermal resistance is 1.6° C/W, the maximum allowable internal power dissipation is

    • Options
    • A. 20 W
    • B. 50 W
    • C. 92 W
    • D. 128 W
    • Discuss
    • 9. The characteristics of a non-linear resistance is i = kv4. If i becomes 100 times, v becomes

    • Options
    • A. about 100 times
    • B. about 10 times
    • C. about 3 times
    • D. about twice
    • Discuss
    • 10. The number of leads in an SCR are :

    • Options
    • A. 2
    • B. 3
    • C. 4
    • D. 5
    • Discuss


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