Mesh-Current Analysis, VCCS with phasors

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The discussion revolves around performing mesh-current analysis using phasors, specifically addressing issues with the calculations involving a voltage-controlled current source (VCCS). The user outlines their mesh equations but finds discrepancies between their results and the expected answers. They detail the derivation of equations for two meshes and the incorporation of a third equation related to the VCCS, leading to a new set of equations. Despite adjustments, the user still struggles with the final values of the currents, indicating a potential misunderstanding of the VCCS application. The conversation highlights the complexities of mesh analysis compared to nodal analysis, emphasizing the importance of correctly integrating the VCCS into the equations.
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http://img247.imageshack.us/img247/7035/problemso9.jpg

Ok so I have to do mesh-current analysis and I think I'm doing it correctly but my answer doesn't match the one given. This has to be done using phasors.

I labeled my meshes from left to right 1, 2, and so on.

Mesh 1:
33.8 = 1I1 + j2I1 + 3(I1 - I2) + (-j5)(I1-I2)
33.8 = 1I1 + j2I1 + 3I1 - 3I2 - j5I1 + j5I2
33.8 = (4 - j3) I1 + (-3 + j5) I2

Mesh 2:
0 = j5(I1 - I2) - 3(I1 - I2) + 2(I2 - I3)
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - 2I3

(mesh current with the VCCS)
I3 = -0.75 Vx
where
Vx = (-j5)(I1 - I2)
I3 = -0.75 * (-j5)(I1-I2)
I3 = j3.75(I1 - I2)

substituting into Mesh 2 equation:
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - 2( j3.75 (I1 - I2) )
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - j7.5(I1 - I2)
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - j7.5I1 + j7.5I2
0 = -3I1 + (5+j2.5)I2

I know:
I = I1

I put both mesh equations in a matrix and the answer isn't what it's displayed in that picture (I get I = I1 = 8.98021 angle -1.828). Am i missing something here? I'm thinking I'm approaching this totally wrong. I always have a hard time with Mesh analysis and always prefer Nodal over it... but I'm almost certain that it has something to do with the VCCS (voltage controlled current source) and my equations for it.
 
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Solved this by simply adding a third equation with
I3 = -0.75 Vx
where
Vx = (-j5)(I1 - I2)
I3 = -0.75 * (-j5)(I1-I2)
I3 = j3.75(I1 - I2)

I3 - (j3.75)I1 + (j3.75)I2 = 0 (third equation)

I put the previous 2 Mesh equations and this one in a matrix and got the values of all 3 currents.

(4 - j3) I1 + (-3 + j5) I2 = 33.8 (mesh 1)
(-3 + j5) I1 + (5 - j5) I2 - (2)I3 = 0 (mesh 2)
(- j3.75)I1 + (j3.75)I2 + I3 = 0 (third equation derived from Vx)

I1 = i = 29 + j2 or 29.07 angle 3.95



In this case this should be corrected:
Mesh 2:
0 = j5(I1 - I2) - 3(I1 - I2) + 2(I2 - I3)
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - 2I3

(mesh current with the VCCS)
I3 = -0.75 Vx
where
Vx = (-j5)(I1 - I2)
I3 = -0.75 * (-j5)(I1-I2)
I3 = j3.75(I1 - I2)

substituting into Mesh 2 equation:
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - 2( j3.75 (I1 - I2) )
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - j7.5(I1 - I2)
0 = j5I1 - j5I2 - 3I1 + 3I2 + 2I2 - j7.5I1 + j7.5I2
0 = -3I1 + (5+j2.5)I2
^ red text not used
 
Last edited:

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