Mesh-Current Analysis, VCCS with phasors

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SUMMARY

The discussion focuses on performing mesh-current analysis using phasors in a circuit with a voltage-controlled current source (VCCS). The user outlines their equations for two meshes and incorporates a third equation derived from the VCCS, leading to the final currents calculated. The user initially struggles with the mesh analysis but ultimately arrives at the correct values for the currents, specifically I1 = 29 + j2 or 29.07 at an angle of 3.95 degrees. The equations used include complex coefficients and adjustments for the VCCS, demonstrating the importance of correctly setting up mesh equations in phasor analysis.

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  • Understanding of mesh-current analysis in electrical circuits
  • Familiarity with phasor representation of AC circuits
  • Knowledge of voltage-controlled current sources (VCCS)
  • Proficiency in complex number arithmetic
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  • Study the application of mesh-current analysis in circuits with multiple sources
  • Learn about the effects of VCCS on circuit behavior and analysis
  • Explore advanced techniques in phasor analysis for AC circuits
  • Practice solving mesh equations using matrix methods and software tools like MATLAB
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Electrical engineering students, circuit designers, and professionals involved in AC circuit analysis and design, particularly those working with mesh-current methods and VCCS applications.

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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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