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Three phase ac network

  1. Jan 31, 2015 #1
    Hi everyone,

    1. The problem statement, all variables and given/known data

    Three inductors with 0.1 H each are delta connected to three phase ac newtork with 220V/50Hz. Determine Iph, IL, P, Q and Theta.

    2. Relevant equations
    Showed at the attempt.

    3. The attempt at a solution

    XL=2*pi*f*L=31.4 ohms
    Iph=Uph/XL=220/31.4=7 A
    IL=1.73*7=12.12 A

    Q=(Iph)^2 XL=Uph Iph sin(theta)

    Since I don't have theta and I need to determine it in thte first place, I shall use he first law.
    Q=(7)^2 31.4=1538.6 VAR
    QT=3*Q=4615 VAR

    Then, I shall substitute the value of Q in the second law to get theta.
    sin^-1 (theta)=Q/Uph Iph=1538.6/220*7=87.55 ْ

    P=Uph Iph cos(theta)=65.65 W
    PT=3*P=196.95 W
  2. jcsd
  3. Jan 31, 2015 #2


    User Avatar

    Staff: Mentor

    Are you sure that you should be seeing real power being dissipated by a purely reactive load? You might want to reconsider what the phase angle must be for such a load.
  4. Feb 6, 2015 #3
    I found out that a purley inductor doesn't disspate any power, which leads to P=0. Thanks :)
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