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Capacitance with an electric shield
Posted Jan 25, 2011, 5:20 p.m. EST Low-Frequency Electromagnetics Version 5.1 3 Replies
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Hello everyone!
I'd like to determine the capacitance between two wires a metal plate inserted between them to act as an electric shield. In the COMSOL 3.3 AC/DC Module 3D Electrostatics Application Mode I set one of the wires to the "port" boundary condition, set the other to "ground," and set the plate to the "electric shielding" boundary condition. The wires and plate are surrounded by a large box with the "zero charge / symmetry" boundary condition applied at its six surfaces. My geometry and an image of my simulation results are attached.
My problem is that the electrostatic potential varies across the surface of the plate. For a conducting metal plate, the potential should be constant everywhere on its surface. Evidently COMSOL is treating the plate as non-conducting.
What boundary conditions must I apply to the plate to ensure it acts as a conducting electric shield? Do I need to use a different application mode?
Thank you!
M. Dyck
P.S. I recognize this problem could likely be simplified to 2D but I will be adding additional geometry objects in the future which necessitate a 3D model.
I'd like to determine the capacitance between two wires a metal plate inserted between them to act as an electric shield. In the COMSOL 3.3 AC/DC Module 3D Electrostatics Application Mode I set one of the wires to the "port" boundary condition, set the other to "ground," and set the plate to the "electric shielding" boundary condition. The wires and plate are surrounded by a large box with the "zero charge / symmetry" boundary condition applied at its six surfaces. My geometry and an image of my simulation results are attached.
My problem is that the electrostatic potential varies across the surface of the plate. For a conducting metal plate, the potential should be constant everywhere on its surface. Evidently COMSOL is treating the plate as non-conducting.
What boundary conditions must I apply to the plate to ensure it acts as a conducting electric shield? Do I need to use a different application mode?
Thank you!
M. Dyck
P.S. I recognize this problem could likely be simplified to 2D but I will be adding additional geometry objects in the future which necessitate a 3D model.
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3 Replies Last Post Jan 31, 2011, 8:22 a.m. EST
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Posted:
1 decade ago
Just a bump.
I'd really appreciate any insights the COMSOL community may be able to share on this issue. This problem is an integral part of my capstone project for my degree, but despite extensive research into COMSOL modeling methodologies I have yet to find a solution.
Is it possible that COMSOL was not designed to handle capacitance calculations when electric shielding is involved?
I'd really appreciate any insights the COMSOL community may be able to share on this issue. This problem is an integral part of my capstone project for my degree, but despite extensive research into COMSOL modeling methodologies I have yet to find a solution.
Is it possible that COMSOL was not designed to handle capacitance calculations when electric shielding is involved?
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Posted:
1 decade ago
Hi,
there are probably not many people using 3.3 any longer. I checked in 3.4 Electrostatics, generalized and didn't find an 'electric shielding' BC. Did you choose 'electric insulation' instead? This would explain your results.Electric insulation does not shield the electric field, it only shields the current field.
To model an electric shield, your plate subdomain must be conducting and you keep it either floating (continuity BC) or you ground it or you apply a potential, Depending on what you want to model.
Cheers
Edgar
there are probably not many people using 3.3 any longer. I checked in 3.4 Electrostatics, generalized and didn't find an 'electric shielding' BC. Did you choose 'electric insulation' instead? This would explain your results.Electric insulation does not shield the electric field, it only shields the current field.
To model an electric shield, your plate subdomain must be conducting and you keep it either floating (continuity BC) or you ground it or you apply a potential, Depending on what you want to model.
Cheers
Edgar
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Posted:
1 decade ago
Hi
in 3.5a I believe there is a floating potential electrode model
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Good luck
Ivar
in 3.5a I believe there is a floating potential electrode model
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Good luck
Ivar