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ECE :: Power Electronics

  1. In a 3 phase full wave regulator feeding resistance load connected in star, the possible range of firing angle a is

  2. A.
    0 ≤ a ≤ 180°
    B.
    0 ≤ a ≤ 150°
    C.
    0 ≤ a ≤ 120°
    D.
    0 ≤ a ≤ 90°

  3. Assertion (A): A dual converter may be circulating current type or non circulating current type.

    Reason (R): In circulating current dual converter only one converter can be operated at one time.

  4. 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

  5. Current chopping leads to

  6. A.
    over voltage
    B.
    over current
    C.
    both over voltage and over current
    D.
    either over voltage or over current

  7. A 3 phase bridge inverter is fed by 400 V battery. The load is star connected and has a resistance of 10 Ω per phase. The peak value of load current is

  8. A.
    40 A
    B.
    20 A
    C.
    10 A
    D.
    5 A

  9. In an SCR, the anode current is controlled by

  10. A.
    gate current only
    B.
    external circuit only
    C.
    both gate current and external circuit
    D.
    none of the above

  11. The rated current of a thyristor is 40 A. The holding current will be about :

  12. A.
    20 A
    B.
    1 A
    C.
    100 mA
    D.
    10 mA

  13. A cycloconverter is

  14. A.
    ac-dc converter
    B.
    dc-ac converter
    C.
    dc-dc converter
    D.
    ac-ac converter

  15. The number of leads in a power semiconductor diode are

  16. A.
    2
    B.
    3
    C.
    4
    D.
    2 or 3

  17. If ton and toff are the turn on and turn off times of a thyristor, then

  18. A.
    ton and toff are almost equal
    B.
    ton >> toff
    C.
    toff >> ton
    D.
    ton is about twice toff

  19. Assertion (A): The gate current of an SCR is always in the form of pulses.

    Reason (R): The gate losses, in pulse triggering, are low.

  20. 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