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Power Electronics problems

  • 1. The power factor at the input terminals of a cyclo- converter is generally

  • Options
  • A. low and leading
  • B. low and lagging
  • C. high and leading
  • D. high and lagging
    • Discuss
  • 2. Modified Mc Murray full bridge inverter uses

  • Options
  • A. 4 thyristors and 2 diodes
  • B. 4 thyristors and 4 diodes
  • C. 8 thyristors and 4 diodes
  • D. 8 thyristors and 8 diodes
    • Discuss
  • 3. A fully controlled bridge converter feeds a highly inductive load such that the load current can be assumed to be constant. The wave shape of input current is

  • Options
  • A. dc
  • B. sinusoidal
  • C. rectangular
  • D. none of the above
    • Discuss
  • 4. The application of gate signal decreases the break over voltage of on SCR.

  • Options
  • A. True
  • B. False
    • Discuss
  • 5. Ripple factor RF and form factor FF are related as

  • Options
  • A. RF = FF2 - 1
  • B. RF = (FF2 - 1)0.5
  • C. RF = FF - 1
  • D. RF = (FF - 1)0.5
    • Discuss
  • 6. In integral cycle control of ac regulator, the input power factor is equal to

  • Options
  • A. duty cycle a
  • B. a2
  • C. a
  • D. (a)1/3
    • Discuss
  • 7. A single phase fully controlled bridge converter is feeding an RLE load. Input voltage is Vm sin ?t and firing angle is a. If average current is I0, then

  • Options
  • A. cos a = RI0 + E
  • B. cos a = RE0 + E
  • C. cos a = E0 - RI0
  • D. cos a = E - RI0
    • Discuss
  • 8. In a 3 phase semiconverter, the output voltage becomes discontinuous for

  • Options
  • A. firing angle > 30°
  • B. firing angle > 60°
  • C. firing angle > 90°
  • D. firing angle > 120°
    • Discuss
  • 9. A static excitation system uses

  • Options
  • A. transformer and thyristors
  • B. transformer and ac exciter
  • C. dc exciter and ac exciter
  • D. transformer and dc exciter
    • Discuss
  • 10. In a semi converter feeding a resistive load

  • Options
  • A. the waveshapes of output voltage and output current are exactly similar
  • B. the waveshapes of output voltage and output current can not be similar
  • C. the waveshapes of output voltage and output current are similar only for low values of firing angle
  • D. the waveshapes of output voltage and output current may be similar or dissimilar
    • Discuss

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