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Power Electronics problems

  • 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. 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
    Electronics and Communication Engineering Power Electronics: In the below figure, the load is highly inductive. The firing angle is a

  • 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
    • Discuss
  • 3. 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
  • 4. A crowbar circuit is generally needed for protection under fault conditions.

  • Options
  • A. True
  • B. False
    • Discuss
  • 5. 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
  • 6. 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
  • 7. 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
  • 8. The number of leads in a DIAC are

  • Options
  • A. 2
  • B. 3
  • C. 4
  • D. 6
    • Discuss
  • 9. An ideal rectifier should have

  • Options
  • A. 100% efficiency, zero ripple factor, zero harmonic factor and unity displacement factor
  • B. 100% efficiency, zero tipple factor, zero harmonic factor and zero displacement factor
  • C. 100% efficiency, zero ripple factor, unity harmonic factor and unity displacement factor
  • D. 100% efficiency, unity ripple factor, zero harmonic factor and unity displacement factor
    • Discuss
  • 10. To turn off an SCR, it is necessary to reduce its current to less than :

  • Options
  • A. trigger current
  • B. holding current
  • C. breakover current
  • D. none of the above
    • Discuss

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