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ECE :: Power Electronics

  1. The number of thyristors in a single phase fully controlled bridge rectifier is

  2. A.
    16
    B.
    8
    C.
    4
    D.
    2

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  3. In a bridge inverter

  4. A.
    an output transformer is essential
    B.
    an output transformer is not essential
    C.
    an output transformer cannot be connected
    D.
    an output transformer, if used, can improve the efficiency of the circuit

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  5. An ideal rectifier should have

  6. 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

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  7. When thyristors are connected in parallel, the current distribution may become non-uniform due to

  8. A.
    inductive effect of current carrying conductors
    B.
    capacitive effect of current carrying conductors
    C.
    both inductive and capacitive effects
    D.
    none of the above

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  9. A single phase fully controlled bridge converter is fed by a voltage Vm sin ωt. The average and rms values of output voltage are

  10. A.
    B.
    C.
    cos a and Vm
    D.
    cos a and 2 Vm

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  11. In a single phase half wave ac regulator feeding a resistive load, the rms load current

  12. A.
    is always positive
    B.
    may be positive or negative
    C.
    is always negative
    D.
    can be even zero

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  13. Which of the following is correct for a BJT?

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  15. In a bridge inverter with single pulse width modulation

  16. A.
    the output frequency is equal to frequency of reference signal
    B.
    the output frequency is equal to frequency of control signal
    C.
    either (a) or (b)
    D.
    neither (a) nor (b)

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  17. In a modified series inverter with two inductors and two capacitors, the load current

  18. A.
    has 2 parallel paths
    B.
    has only one parallel path
    C.
    can have three parallel paths
    D.
    has four parallel paths

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  19. The number of layers in a Shockley diode are

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

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