Superposition theorem problem

Discussion in 'General Electronics Chat' started by xxxyyy, May 5, 2012.

  1. xxxyyy

    Thread Starter Member

    Oct 7, 2011
    34
    1
    Hi!
    I tried to solve AC circuit using Superposition theorem,but I have problem. My circuit is below.
    Code ( (Unknown Language)):
    1. http://imageshack.us/f/696/circuits.jpg/
    As you can see, phase angle of Voltage source is 90 degrees and phase angle of Current source is 30 degrees.
    Firstly, I replaced Current source with open circuit and I solved circuit, picture below.
    Code ( (Unknown Language)):
    1. http://imageshack.us/f/641/circuit1l.jpg/
    I got this:
    I1' = -0.1307 + 0.3864j, Effective value = 0.4079A
    I2' = -0.2035 + 0.3432j, Effective value = 0.3990A
    I3' = 0.0729 + 0.0432j, Effective value = 0.0847A.
    I checked my results using Multisim and they seem to be correct.
    Then, I replaced Voltage source with short circuit and I solved circuit, picture below.
    Code ( (Unknown Language)):
    1. http://imageshack.us/f/29/circuit2r.jpg
    I got this:
    I1" = -0.7435 + 3.2408*j, Effective value = 3.3250A,
    I2" = 0.3718 - 1.6204*j, Effective value = 1.6625A,
    I3" = -0.3440 - 0.0789*j, Effective value = 0.3529A.
    I checked my results using Multisim and they seem to be correct.
    Superposition says that:

    I1=I1'+I1" = (-0.1307+0.3864j)+(-0.7435+3.2408*j)=-0.8742+3.6272*j, Effective value = 3.7311A,

    I2=I2'+I2" = (-0.2035+0.3432j)+(0.3718-1.6204*j)=0.1683-1.2772*j, Effective value = 1.2882A,

    I3=I3'+I3" = (0.0729+0.0432j)+(-0.3440-0.0789*j)=-0.2711-0.0357*j, Effective value = 0.2734A.

    Multisim says that Effective values are different, picture below.
    Code ( (Unknown Language)):
    1. http://imageshack.us/f/171/circuit3y.jpg
    Does anyone know where did I make mistake?
     
    Last edited: May 5, 2012
  2. xxxyyy

    Thread Starter Member

    Oct 7, 2011
    34
    1
    I've found mistake :) Solved.
     
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