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ECE :: Power Electronics

Power Electronics - Section 1
Power Electronics - Section 2
Power Electronics - Section 3
Power Electronics - Section 4
Power Electronics - Section 5
Power Electronics - Section 6
Power Electronics - Section 7
Power Electronics - Section 8
Power Electronics - Section 9

  1. In brushless excitation system of modern alternators, the main exciter is

    2. A.
    dc generator
    B.
    ac generator
    C.
    either dc or ac generator
    D.
    induction generator

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  2. The two-transistor model of a thyristor consists of two transistors :

    3. A.
    one n-p-n and other p-n-p
    B.
    both p-n-p
    C.
    both n-p-n
    D.
    one n-p-n and other UJT

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  3. In a thyristor, the forward breakover voltage

    4. A.
    is constant
    B.
    may be constant or may depend on gate current
    C.
    decreases as gate current is increased
    D.
    increases as gate current is increased

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  4. The gate lead, in a thyristor is welded to :

    5. A.
    p layer to which anode is connected
    B.
    n layer nearest to the anode terminal
    C.
    p layer nearest to the cathode terminal
    D.
    outside n layer

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  5. In a 3 phase full converter, the firing angle is less than 60°. The instantaneous output voltage

    6. A.
    will have positive part only
    B.
    will have both positive and negative parts
    C.
    may have both positive and negative parts
    D.
    will have negative part if load is inductive

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  6. In a stud mounted SCR, the stud is

    7. A.
    in thermal contact with heat sink
    B.
    insulated from heat sink
    C.
    in electrical and thermal contact with heat sink
    D.
    in either electrical or thermal contact with heat sink

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  7. In pulse width modulation of chopper

    8. A.
    T is kept constant and Ton is varied
    B.
    Ton is kept constant T is varied
    C.
    both T and Ton are varied
    D.
    either T or Ton is varied

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  8. In a full bridge inverter, the waveshape of load current depends on

    9. A.
    relative values of load parameters R, L and C
    B.
    relative values of load parameters R and L
    C.
    relative values of load parameters L and C
    D.
    gating frequency

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  9. The characteristics of which device has peak point and valley point

    10. A.
    SCR
    B.
    PUT
    C.
    SCS
    D.
    Shockley diode

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  10. In a step down chopper using time ratio control, the input voltage is V and duty cycle is a. The load is purely resistive having resistance R. The average and rms load currents are

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