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Use of Impedance Boundary condition in AC/DC module
Posted Jan 8, 2010, 4:03 p.m. EST 2 Replies
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I am trying to model the electromagnetic field of a conductor carrying high frequency current where the skin depth is very small in relation to the conductor cross-section. Due to the geometry it is necessary to model this in 3D. Following advice in the help, I decided to use the impedance boundary condition (saving elements) which means deactivating the space occupied by the wire. I have imposed 1 Volt on the live cross-sectional 'face' of one end of the wire and grounded the other 'face'. These 'faces' actually belong to the surrounding air (since the interior of the conductor is no longer part of the computational domain space). Has anyone built anything similar. Is this the correct way to drive the model? Or should the voltages be applied to the circular 'edges' of the two faces. Any comments from anyone, would be gratefully received.
2 Replies Last Post Jan 11, 2010, 4:35 p.m. EST
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Posted:
1 decade ago
Hi
I'm not sur if I understand fully the model you describe, but my thoughts would be to apply the voltage/currents on the "edges" of the cylinder (I assume this is the shape) that represents the conductor, that now is only a "skin".
So I would not use faces or "boundaries" as defined in COMSOL for 3D, rather the edges.
Good luck
Ivar
I'm not sur if I understand fully the model you describe, but my thoughts would be to apply the voltage/currents on the "edges" of the cylinder (I assume this is the shape) that represents the conductor, that now is only a "skin".
So I would not use faces or "boundaries" as defined in COMSOL for 3D, rather the edges.
Good luck
Ivar
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Posted:
1 decade ago
Thanks Ivar,
I can explain my reason for asking this question. When the live and earth 'faces' or indeed 'boundaries' (when the impedance boundary condition is activated) of the 3D conductor are not exterior faces and are separated by air, does the Comsol solution have physical meaning ? It does seem to produce a realistic solution when the air gap between the live and earth is small but have we not violated div.J = 0 where the live and earth are imposed ? i.e. current emerges magically from the live end of the wire and terminates on the earth. Or possibly the software is introducing displacement current ? One way I thought of getting around the problem is to introduce an _interior_ void region connecting the live and earth on which 'magnetic insulation' is imposed. This would complete the circuit and would play the role of an infinitely conducting connector between live and earth. If you have any thoughts/comments these would be gratefully received.
I can explain my reason for asking this question. When the live and earth 'faces' or indeed 'boundaries' (when the impedance boundary condition is activated) of the 3D conductor are not exterior faces and are separated by air, does the Comsol solution have physical meaning ? It does seem to produce a realistic solution when the air gap between the live and earth is small but have we not violated div.J = 0 where the live and earth are imposed ? i.e. current emerges magically from the live end of the wire and terminates on the earth. Or possibly the software is introducing displacement current ? One way I thought of getting around the problem is to introduce an _interior_ void region connecting the live and earth on which 'magnetic insulation' is imposed. This would complete the circuit and would play the role of an infinitely conducting connector between live and earth. If you have any thoughts/comments these would be gratefully received.