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ECE :: Power Electronics

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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 a modified series inverter

    2. A.
    the maximum output frequency is less than frequency of damped oscillations
    B.
    the output frequency can be even higher than the frequency of damped oscillations
    C.
    the output frequency cannot exceed the frequency of damped oscillations
    D.
    any of the above

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  2. Assertion (A): Light triggering is very suitable for HVDC transmission.

    Reason (R): Light triggering has the advantage of complete electrical isolation of gate circuit.

    3. 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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  3. Class A and class B chopper

    4. A.
    operate in first quadrant
    B.
    operate in second quadrant
    C.
    class A chopper operates in first quadrant while class B operates in second quadrant
    D.
    may operate in either first or second quadrant

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  4. To turn off an SCR, it is necessary to reduce its current to less than :

    5. A.
    trigger current
    B.
    holding current
    C.
    breakover current
    D.
    none of the above

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  5. When a single phase dual converter is operating in circulating current mode

    6. A.
    both converters are working as rectifiers simultaneously
    B.
    one converter is always working as rectifier and the other as inverter
    C.
    only one converter is working at one time
    D.
    both converters are either working as rectifiers or as inverters simultaneously

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  6. The load circuit of a single phase full bridge inverter

    7. A.
    must be underdamped
    B.
    must be overdamped
    C.
    may be underdamped or overdamped
    D.
    may be any type of load

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  7. When an SCR is reverse biased

    8. A.
    two junctions are reverse biased and one junction is forward biased.
    B.
    all the three junctions are reverse biased.
    C.
    one junction is reverse biased and two junctions are forward biased.
    D.
    any of the above depending on the magnitude of reverse bias.

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  8. A dc series motor is coupled to a load whose torque is proportional to speed. It is fed by a single phase ac supply through a full converter. When speed is 500 rpm, firing angle is 45°. It is desired to raise the speed. It will be necessary to

    9. A.
    decrease the firing angle
    B.
    increase the firing angle
    C.
    either decrease or increase the firing angle depending on the required speed
    D.
    decrease the load torque

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  9. In Jone chopper, the commutating element

    10. A.
    is a capacitor
    B.
    is a capacitor and an inductor
    C.
    is a capacitor and an auto transformer
    D.
    none of the above

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  10. A LASCR has

    11. A.
    4 semiconductor layers and 3 junctions
    B.
    3 semiconductor layers and 2 junctions
    C.
    2 semiconductor layers and 2 junctions
    D.
    any of these depending on the rating

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