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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. As compared to a p-n junction diode

    2. A.
    a schottky diode has lower cut in voltage and lower reverse saturation current
    B.
    a schottky diode has higher cut in voltage and higher reverse saturation current
    C.
    a Schottky diode has lower cut in voltage and higher reverse saturation current
    D.
    a schottky diode has higher cut in voltage and lower reverse saturation current

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  2. From which instant is the turn off time of a thyristor defined

    3. A.
    when anode voltage becomes zero
    B.
    when anode current becomes zero
    C.
    when both anode voltage and current become zero
    D.
    none of the above

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  3. In a single phase cycloconverter with centre tapped transformer

    4. A.
    all thyristors carry currents for equal duration
    B.
    the durations of currents in all thyristors may or may not be equal
    C.
    the durations of currents in all thyristors cannot be equal
    D.
    the duration of currents in all thyristors must be equal for satisfactory operation

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  4. If Ar and Ac are the amplitudes of reference and control signals, the modulation index M is

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  5. Thyristors can be used for control of

    6. A.
    dc separately excited motor
    B.
    dc shunt motor
    C.
    dc series motor
    D.
    all of the above

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  6. Assertion (A): Thyristors can be used in controlled heating, excitation systems of alternators, speed control of motors and HVDC

    Reason (R): A static var system using thyristors is very commonly used in high voltage ac systems.

    7. 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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  7. In a dual converter operated in circulating current mode, the circulating current flows

    8. A.
    when load current is zero
    B.
    when load current is non-zero
    C.
    even when load current is zero
    D.
    none of the above

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  8. For a single phase half wave converter feeding a resistive load, the firing angle a. The waveshape in below figure is for

    9. A.
    output voltage
    B.
    input voltage
    C.
    voltage drop across thyristor
    D.
    none of the above

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  9. A class B chopper operates in third quadrant.

    10. A.
    True
    B.
    False

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  10. In a full bridge circuit supplying an RLC under damped circuit

    11. A.
    the waveshapes of output voltage and load current are square
    B.
    the waveshapes of output voltage and load current are sinusoidal
    C.
    the waveshapes of output voltage is square but the waveshape of load current is nearly sinusoidal
    D.
    none of the above

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