# 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.