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ECE :: Power Electronics

  1. The number of doped regions in a SCR is

  2. A.
    2
    B.
    3
    C.
    4
    D.
    5

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  3. All inverters use forced commutation.

  4. A.
    True
    B.
    False

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  5. In 180° mode of operation of a 3 phase bridge inverter, two thyristors conduct at one time.

  6. A.
    True
    B.
    False

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  7. In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then

  8. A.
    average thyristor current will be less than 20 A but rms thyristor current will be more than 20 A
    B.
    both the average and rms thyristor currents will be less than 20 A
    C.
    both the average and rms thyristor currents will be more than 20 A
    D.
    rms thyristor current will be 20 A and average thyristor current will be 10 A

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  9. A reactor is used in a dual converter operating in non-circulating current mode.

  10. A.
    True
    B.
    False

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  11. Which of these commutation methods uses an auxiliary SCR?

  12. A.
    Class A
    B.
    Class B
    C.
    Class C
    D.
    Class D

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  13. A thyristor needs protection against

  14. A.
    high
    B.
    high
    C.
    both high and high
    D.
    either high or high

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  15. Two semiconverters are connected in series to form a single phase series converter. The input v = Vm sin ωt and a1 = a2 are the firing angles of the two converters. If a1 = a2 = 0, the dc output voltage is

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  17. In integral cycle control the period of on-off control should be more than mechanical time constant of load.

  18. A.
    True
    B.
    False

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  19. A single phase half wave converter is feeding a resistive load. Just before triggering, the voltage across thyristor is

  20. A.
    zero
    B.
    about 1 V
    C.
    same as input voltage
    D.
    twice the input voltage

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