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ECE :: Power Electronics

  1. 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 thyristor current is


  2. The main utility of SCR is due to

  3. A.
    gate triggering
    B.
    high temperature triggering
    C.
    triggering
    D.
    high breakdown voltage

  4. In a single phase full wave ac regulator the firing angles during both half cycles are equal.

  5. A.
    True
    B.
    False

  6. In a 3 phase full wave regulator feeding a star connected resistance load, firing angle is 75°. Then the number of thyristors conducting at one time is

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

  8. The symbol in figure is for

  9. A.
    SUS
    B.
    SBS
    C.
    Shockley diode
    D.
    UJT

  10. The turn on characteristics of a power transistor can be assumed to be linear, as shown in the below figure . During turn on time T, voltage reduces linearly from V to 0 and current rises linearly from 0 to I. The energy loss during time T is

  11. A.
    VIT
    B.
    C.
    D.

  12. The circuit in figure is for

  13. A.
    resonant commutation
    B.
    self commutation
    C.
    load commutation
    D.
    auxiliary commutation

  14. A single phase half bridge inverter required to feed R-L loads needs

  15. A.
    2 thyristors
    B.
    4 thyristors
    C.
    2 thyristors and two diodes
    D.
    4 thyristors and 4 diodes

  16. Typical values of for an SCR are in the range of

  17. A.
    1 to 10
    B.
    25 to 500
    C.
    0.1 to 1
    D.
    1000 to 2000

  18. When a dc chopper feeds an RLE load, the load current, during steady state operation

  19. A.
    remains constant
    B.
    varies between maximum and minimum values
    C.
    may remain constant or vary
    D.
    is constant if R is constant