power factor correction

Discussion in 'Homework Help' started by teesside_jam, Mar 3, 2011.

  1. teesside_jam

    Thread Starter New Member

    Mar 3, 2011
    hi all newbi to the site and have tried to find what i needed but seem to have got stuck again, i will list the question below and me workings out


    3) Power factor correction
    Construct the circuit of Figure 1(top pic). The line voltage on load is 11kV, the phase impedance is ​
    Z = 120 + j160W,​

    f = 50Hz, C1 = C2 = C3 = 4.8μF.
    R=120 L=509mH

    a) Measure the line currents before and after adding capacitors C​
    1, C2 and C3.​

    What is the implication if there is a change in the currents?​

    Calculate the power factor before and after inserting the capacitors.​

    Draw a phasor diagram to aid the power factor correction.
    b) Calculate the capacitance to be inserted between the load lines if the power factor is corrected as is
    1), and verify your answer by measurement.
    c) Calculate the capacitances which need to be added to the phase circuit and to the load lines if the​

    power factor is corrected to 0.9. What do you observe from the comparison?

    worked out my line currents to be 44.74A withou the capacitors , and 34.29 A with them

    first i started by getting inductive reactance
    XL = 2*pi*50*0.509
    XL= 159.91 (2dp)

    Z= sqrt(R^2*XL^2)
    Z= 199.93

    phase angle
    A= tan^-1 (XL/R)
    A= tan^-1 (199.93/120)
    A= 53.15 (2dp)

    power factor
    0.60 (2dp)

    now i think i have calculated the PF before the capacitors were added , but how did i do the calculations with capacitors.

    Note i also noticed that the line voltage wasnt 11kv as stated when i simulated it, but i will stick to it as that what has been specified.

    any help would be great thanks james