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  • Question
  • Which of these triggering methods for series connected SCRs use LASCR in the gate circuit?


  • Options
  • A. Resistance triggering
  • B. Simultaneous triggering
  • C. Sequential triggering
  • D. Optical triggering

  • Correct Answer
  • Optical triggering 

    Explanation
    Optical triggering uses LASCR.

    Power Electronics problems


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    • 1. A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the number of thyristors in parallel is

    • Options
    • A. 3
    • B. 4
    • C. 6
    • D. 10
    • Discuss
    • 2. A single phase half wave controlled rectifier circuit is feeding on RL load. The circuit has a freewheeling diode. The input voltage is v = Vm sin ?t. If I0 is the load current during the conduction of freewheeling diode, the KVL equation during the conduction of free wheeling diode is

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 3. A 3 phase bridge inverter is fed by 400 V battery. The load is star connected and has a resistance of 10 ? per phase. The peak value of load current is

    • Options
    • A. 40 A
    • B. 20 A
    • C. 10 A
    • D. 5 A
    • Discuss
    • 4. During forward blocking state of SCR, the voltage and current respectively are

    • Options
    • A. high and high
    • B. low and low
    • C. high and low
    • D. low and high
    • Discuss
    • 5. A cycloconverter is

    • Options
    • A. ac-dc converter
    • B. dc-ac converter
    • C. dc-dc converter
    • D. ac-ac converter
    • Discuss
    • 6. In a series inverter supplying a load resistance R, the commutating elements L and C should be such that

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 7. An RC snubber circuit is used to protect a thyristor against :

    • Options
    • A. false triggering
    • B. failure to turn on
    • C. switching transients
    • D. failure to commutate
    • Discuss
    • 8. In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then

    • Options
    • 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
    • Discuss
    • 9. A 3 phase ac regulator uses

    • Options
    • A. 3 thyristors
    • B. 6 thyristors
    • C. 9 thyristors
    • D. 12 thyristors
    • Discuss
    • 10. HVDC transmission systems generally use

    • Options
    • A. 12 pulse converters
    • B. 6 pulse converters
    • C. 3 pulse converters
    • D. either 12 or 6 pulse converters
    • Discuss


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