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Lecture 4:
Mesh Current Analysis & Source
Transformation
Nilsson 4.5-4.9
ENG17 : Circuits I
Spring 2015
April 9, 2015
1
Overview
• Mesh-Currents
• Mesh-Current
w/Dependent Source
• Special Cases
• Node-Voltage vs.
Mesh-Current
• Source
Transformations
2
Go Mesh or Go Home
• Mesh = loop with no other loops inside it
• Mesh-Current Method needs [be – (ne – 1)]
equations
• Planar circuits only
• Mesh current = current that exist only in
the perimeter of a mesh
• Mesh current ≠ Branch current
– maybe
3
Mesh Currents
4
Evolution
Branch Currents
Mesh Currents
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Strategy for Mesh-Current Analysis
1. Assign mesh currents.
2. Apply KVL to each mesh.
– Use Ohm’s law to express voltages in terms
of mesh currents
3. Solve the resulting simultaneous
equations to get mesh currents.
4. Use mesh currents to find branch
currents and/or any other parameter.
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Example
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Overview
• Mesh-Currents
• Mesh-Current
w/Dependent Source
• Special Cases
• Node-Voltage vs.
Mesh-Current
• Source
Transformations
8
(Don’t) Mesh It Up
9
Overview
• Mesh-Currents
• Mesh-Current
w/Dependent Source
• Special Cases
• Node-Voltage vs.
Mesh-Current
• Source
Transformations
10
Mesh with Current Source
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Supermesh…Super Cool
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Example
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Example
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Overview
• Mesh-Currents
• Mesh-Current
w/Dependent Source
• Special Cases
• Node-Voltage vs.
Mesh-Current
• Source
Transformations
15
Node…Mesh…and all the rest
•
•
•
•
Why are we here?
Difficult answer
Try to make life easier
Supernodes or supermeshes?
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Comparison
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Overview
• Mesh-Currents
• Mesh-Current
w/Dependent Source
• Special Cases
• Node-Voltage vs.
Mesh-Current
• Source
Transformations
18
Source Transformations
• Akin to series / parallel reductions and
delta-to-wye transformation
• Allows a voltage source with resistor in
series to be replaced by current source in
parallel with same resistor
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Additional Elements
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Recap
• Mesh-Currents
• Mesh-Current
w/Dependent Source
• Special Cases
• Node-Voltage vs.
Mesh-Current
• Source
Transformations
21
Example
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Example
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Example
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