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ECE :: Power Electronics

  1. If the frequency is less than the damped frequency in a series- inverter

  2. A.
    the distortion of output voltage waveform is low
    B.
    the distortion of output voltage waveform is high
    C.
    the distortion of output voltage may be high or low depending on the load impedance
    D.
    none of the above

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  3. The output frequency of a cycloconverter can be changed by changing the firing angle.

  4. A.
    True
    B.
    False

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  5. Mc Murray full bridge inverter uses

  6. A.
    4 thyristors and 2 diodes
    B.
    4 thyristors and 4 diodes
    C.
    8 thyristors and 4 diodes
    D.
    8 thyristors and 8 diodes

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  7. Assertion (A): A DIAC has four layers but only two terminals.

    Reason (R): A DIAC can conduct in both directions.

  8. 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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  9. In a 3 phase full converter, the instantaneous output voltage can have negative part if

  10. A.
    firing angle is less than 60°
    B.
    firing angle is less than 90°
    C.
    firing angle is more than 60°
    D.
    firing angle is more than 90°

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  11. In a single phase full wave ac regulator using two thyristors only, the gate circuits of the two thyristors

  12. A.
    must be isolated
    B.
    may or may not be isolated
    C.
    should be preferably, isolated
    D.
    should not be isolated

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  13. The circuit in figure is for

  14. A.
    resonant commutation
    B.
    line commutation
    C.
    auxiliary commutation
    D.
    complementary commutation

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  15. A fully controlled bridge converter is feeding an RLE load. For some circuit conditions firing angle is 47°. If connections of battery are reversed, the firing angle is likely to be

  16. A.
    47°
    B.
    less than 47°
    C.
    more than 47°
    D.
    either more or less than 47°

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  17. In a single phase half wave converter feeding resistive load and full wave converter (M - 2 connection) feeding a resistive load the circuit conditions are similar. The firing angle is a. Then the waveshapes of voltages across thyristors

  18. A.
    are similar
    B.
    are not similar
    C.
    may be similar or dissimilar
    D.
    are similar only for some values of a

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  19. In a 3 phase full converter feeding a highly inductive load, the average load current is 150 A. The peak current through thyristor is

  20. A.
    150 A
    B.
    75 A
    C.
    50 A
    D.
    300 A

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