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Capacitor needed for phase angle change (RLC network)

  1. Feb 10, 2015 #1
    1. The problem statement, all variables and given/known data
    An inductive load is connected to a 120V (rms), 60Hz AC source. The load draws 5.0 kW at a power factor of 0.81 (lagging). You need to improve your power factor to 0.96 (lagging) by adding a capacitor.

    What is the Capacitance needed (in uF)?

    2. Relevant equations
    P/|S| = cos(phi)
    Q = V^2/X
    S = sqrt(P^2 + Q^2)

    3. The attempt at a solution
    Please see photo with my solution attached. My professor says the answer is actually 398.17uF. I did this problem multiple times and never got that answer. I keep getting what I got in the photo attached (271uF).

    Attached Files:

  2. jcsd
  3. Feb 10, 2015 #2


    User Avatar

    Staff: Mentor

    It's hard to make out your work in that sideways photo. Can you explain your approach?
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