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ECE :: Power Electronics

  1. In a circuit using a full wave converter (M - 2 connection) the PIV of each thyristor is 400 V. For the same output voltage and fully controlled bridge converter, PIV will be

  2. A.
    400 V
    B.
    800 V
    C.
    200 V
    D.
    2002 V

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  3. A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When a = 0, speed is 500 rpm. If a = 45°, the speed is likely to be

  4. A.
    about 350 rpm
    B.
    about 250 rpm
    C.
    about 175 rpm
    D.
    about 125 rpm

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  5. In a multiphase chopper, all choppers operate together.

  6. A.
    True
    B.
    False

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  7. The terminals of a power MOSFET are called

  8. A.
    emitter, base, collector
    B.
    source, gate, drain
    C.
    source, base, drain
    D.
    emitter, gate, drain

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  9. Assertion (A): The surge current which an SCR can withstand is much higher than rms on state current.

    Reason (R): The duration of surge current is very small.

  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. A single phase half wave controlled rectifier circuit has a free wheeling diode. The load is a combination of R and L. The firing angle is a. The period of conduction of SCR and free wheeling diode respectively are

  12. A.
    a < ωt < p and p < ωt < (2p + a)
    B.
    a < ωt < p and p < ωt < 2p
    C.
    a < ωt < (p + a) and (p + a) < ωt < 2p
    D.
    a < ωt < p and p < ωt < (2p - a)

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  13. Assertion (A): A transistor requires a continuous base signal for conduction but a thyristor requires a gate pulse.

    Reason (R): Transistor find widespread application in power electronic circuits.

  14. 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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  15. In a thyristor the gate current is increased, then

  16. A.
    anode current will increase
    B.
    anode current will decrease
    C.
    anode current will remain constant
    D.
    anode current may increase or decrease

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  17. Thyristors are not suitable for logic circuits.

  18. A.
    True
    B.
    False

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  19. A single phase half wave rectifier is feeding a resistive load. Input voltage v = Vm sin ωt. The output dc voltage is Vdc and output rms voltage is Vrms . If firing angle is 180°, Vdc and Vrms respectively are

  20. A.
    0 and 0
    B.
    C.
    0 and - Vm
    D.

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