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ECE :: Power Electronics

  1. The number of leads in an SCR are :

  2. A.
    2
    B.
    3
    C.
    4
    D.
    5

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  3. In a single phase full wave converter (M-2 connection) feeding on R - L load, the input voltage is v = Vm sin ωt. The expression for dc output voltage is

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  5. A thyristor has a turn on time of 6 μs. If the anode circuit is inductive, the turn on time will be

  6. A.
    6 μs
    B.
    less than 6μs
    C.
    more than 6 μs
    D.
    either 6 μs or less

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  7. The total number of leads in reverse conducting thyristor is

  8. A.
    2
    B.
    3
    C.
    1
    D.
    4

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  9. 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.

  10. 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

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  11. If Vdc1 is the dc output voltage in half wave controlled rectifier circuit feeding resistive load and Vdc2 is the dc output voltage in full wave controlled rectifier circuit (M - 2 connection) feeding resistive load, then

  12. A.
    Vdc1 = 0.5 Vdc2 for all values of firing angle
    B.
    Vdc1 = Vdc2 for all values of firing angle
    C.
    Vdc1 ≤ 0.5 Vdc2 for all values of firing angle
    D.
    Vdc1 ≥ 0.5 Vdc2 for all values of firing angle

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  13. A semi converter operates in two quadrants.

  14. A.
    True
    B.
    False

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  15. Figure shows a chopper feeding RLE load, The free wheeling diode conducts when

  16. 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

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  17. Assertion (A): An ideal rectifier should have unity harmonic factor

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

  18. 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

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  19. A single phase half wave rectifier is feeding a resistive load. When a = 0, dc output voltage is 127 V. When a = 30°, the dc output voltage will be about

  20. A.
    127 V
    B.
    120 V
    C.
    110 V
    D.
    100 V

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