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Single Phase Full Wave Controlled Bridge Rectifier

  1. Jan 6, 2015 #1
    1. The problem statement, all variables and given/known data

    For a bridge rectifier (4 thyristor) feeding an RL load having infinite inductance (to assume constant current) and a 100 ohm resistance, calculate for firing angles of 90°, 120° & 150° the average DC voltage and current. The bridge supply is 200V RMS. Draw Waveforms of load voltage, thyristor currents & supply current.

    2. Relevant equations

    Vav = 2Vm/PI * Cos(α).

    Iav = Vav/R

    3. The attempt at a solution

    90°

    Vav = (sqrt(2) * 200)/PI * cos(90) = 0.0V

    Iav = 0A

    120°

    Vav = (sqrt(2) * 200)/PI * cos(120) = -45.01V

    Iav = -45.01/100 = 0.4501A

    150°

    Vav = (sqrt(2) * 200)/PI * cos(150) = -77.97V

    Iav = -77.97/100 = 0.7797A

    I understand how the waveforms for the voltage should be but in the book solutions, for 90° firing angle, it shows a positive current for each thyristor, whereas the average value calculated is 0.0A hence it would be suggested that there should be no current. Also, for the firing angles of 120 & 150, should the current be inverted in terms of the currents for 30 and 60 degrees where the current is the positive value of the values for 150 and 120 respectively?
     
  2. jcsd
  3. Jan 7, 2015 #2

    gneill

    User Avatar

    Staff: Mentor

    I think you'll want to integrate over a period to find the average values. Perhaps you might begin by sketching the load voltage or current for one of the firing angle cases.
     
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