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  • Question
  • In the below figure, the load is highly inductive. The firing angle is a for each of the thyristors. The periods of conduction of Th1 and Th2 respectively are
    In the below figure, the load is highly inductive. The firing angle is a for each of the thyristors.


  • Options
  • A. 0 to p and p to 2p
  • B. a to p and p + a to 2p
  • C. a to p + a and p + p to 2p + a
  • D. a to p - a and p + a to 2p - a

  • Correct Answer
  • a to p + a and p + p to 2p + a 


  • Power Electronics problems


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    • 1. A rectifier is fed by a transformer. The rms voltage and current at secondary of transformer are Vs and Is. Output dc power is Vdc Idc and output ac power is (Vrms ) (Irms), Transformer utilisation factor TUF is

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 2. A single phase full wave regulator feeds a resistive load. The firing angle of thyristors is 90°. The input power factor is

    • Options
    • A. 1
    • B. 0.707 lagging
    • C. 0.5 lagging
    • D. 0.2 lagging
    • Discuss
    • 3. In a parallel inverter the turn off time tq of thyristor and values of commutating elements L and C are related as

    • Options
    • A. tq = pLC
    • B. tq = LC
    • C. tq = LC
    • D. tq = LC
    • Discuss
    • 4. In a full bridge single phase inverter feeding RLC load

    • Options
    • A. one thyristor and one diode conduct simultaneously
    • B. two thyristors conduct simultaneously
    • C. two thyristors or two diodes conduct simultaneously
    • D. four thyristors conduct simultaneously
    • Discuss
    • 5. Which of the following commutation methods is the overall circuit under damped?

    • Options
    • A. Class A
    • B. Class B
    • C. Class C
    • D. Both class A and Class B
    • Discuss
    • 6. A single phase semiconverter is feeding a highly inductive load and has a freewheeling diode across the load. The waveshape of input current is

    • Options
    • A. sinusoidal
    • B. rectangular
    • C. sinusoidal or rectangular
    • D. triangular
    • Discuss
    • 7. A crowbar circuit is generally needed for protection under fault conditions.

    • Options
    • A. True
    • B. False
    • Discuss
    • 8. A single phase fully controlled bridge converter is fed by a voltage Vm sin ?t. The average and rms values of output voltage are

    • Options
    • A.
    • B.
    • C. cos a and Vm
    • D. cos a and 2 Vm
    • Discuss
    • 9. In a bridge inverter

    • Options
    • A. an output transformer is essential
    • B. an output transformer is not essential
    • C. an output transformer cannot be connected
    • D. an output transformer, if used, can improve the efficiency of the circuit
    • Discuss
    • 10. In a modified series inverter with two inductors and two capacitors, the load current

    • Options
    • A. has 2 parallel paths
    • B. has only one parallel path
    • C. can have three parallel paths
    • D. has four parallel paths
    • Discuss


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