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  • Question

  • A Shockley diode can be used


  • Options
  • A. in place of SCR
  • B. as a trigger switch for SCR
  • C. in place of UJT
  • D. both in place of SCR and as a trigger switch for SCR

  • Correct Answer
  • as a trigger switch for SCR 

    Explanation
    It is a four layered PNPN device without a gate terminal. Its characteristics is similar to that of SCR with zero gate current. It is acting as a trigger switch for Thyristor.

    Power Electronics problems

    Search Results

    • 1. A single phase full converter gives maximum and minimum output voltage at firing angles of

    • Options
    • A. 0 and 180° respectively
    • B. 180° and 0° respectively
    • C. 0 and 90° respectively
    • D. 90° and 0° respectively
      • Discuss
    • 2. In controlled heating circuits, thyristors act as

    • Options
    • A. rectifier
    • B. inverter
    • C. ac regulator
    • D. chopper
      • Discuss
    • 3. On load tap changer using thyristors can have a maximum of two taps.

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. In a single phase full bridge converter (B - 2 connection), the input voltage is v = Vm sin ?t. The output dc voltage for resistive load

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 5. A single phase electric heater uses phase controlled thyristors. The firing angle is 90°. The degree of heating is

    • Options
    • A. 25% of maximum
    • B. 50% of maximum
    • C. 75% of maximum
    • D. none of the above
      • Discuss
    • 6. As regards single phase dual converter

    • Options
    • A. the change in operation from one quadrant to the other is faster in non-circulating current mode
    • B. the change in operation from one quadrant to the other is faster in circulating current mode
    • C. the time response to change in operation from one quadrant to other is the same in both the modes
    • D. the time response to change in operation from one quadrant to the other may be faster in any of the two modes
      • Discuss
    • 7. In a parallel inverter

    • Options
    • A. the commutating capacitor C is across the primary of transformer and the load is across the secondary
    • B. the commutating capacitor and load are connected across the secondary of transformer
    • C. the commutating capacitor C and load are connected in series and the combination is across the secondary of transformer
    • D. none of the above
      • Discuss
    • 8. In a fully controlled bridge converter feeding a resistive load the waveshapes of output voltage and output current

    • Options
    • A. are always similar
    • B. can never be similar
    • C. may be similar or dissimilar
    • D. are similar only if a = 0
      • Discuss
    • 9. Assertion (A): Snubber circuit has an RC series circuit in parallel with SCR

      Reason (R): Voltage across a capacitor can not change instantaneously.


    • Options
    • 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
      • Discuss
    • 10. Which of these commutation methods is used in AC-DC converters?

    • Options
    • A. Class A
    • B. Class C
    • C. Class D
    • D. Class F
      • Discuss

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