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Skin effect error
Posted Dec 30, 2011, 1:28 p.m. EST Low-Frequency Electromagnetics Version 4.0a 3 Replies
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I have problem in simulating induced current in the cross section of a wire which is copper. The problem is that based on the skin effect theory the current must be in one direction in the outer cross section of the wire and when we go to inner cross section, its density must fall, but my simulations show that the current is in one direction in the outer cross section and in the opposite direction in the inner cross section. I mean when we go from outer cross section to inner cross section the direction of the current changes alternatively.
I have attached the 2D model which I have created to explain the issue. In this model I have exited just one infinite wire of copper by external current density and 13MHz frequency but when simulate this wire I get the alternating current from outer cross section to inner cross section.
I also see the same problem in simulating two loop problem in which I have excited the first loop by external current density boundary condition and wanted to see current density of the second loop.
Thank you
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are you sure you model is complete ? you are in 2D (not 2D axi) solving for only out of plane vector component, so you have a infinite long wire of copper, no air/domain around so your field is not looping even in any vacuum outside of your copper. And as you have no "return in curent".
For me with that you can only get a cylindrical solution, as you see it, no ?
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Good luck
Ivar
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With previous model I just wanted to say that even in this simple example (just one infinite), I do not get the right answer. What can I do to make it right?
I have attached the original model in which I have forced the upper loop to have current by external current density boundary condition and set its material to air to avoid this problem (alternating current from outer cross section to inner cross section), but in the bottom loop in which I wanted to see the induced current and its material is set to copper, I see the alternating current as I said before. For your information I use magnetic fields interface, make the entire mesh extremely fine and make the bottom loop mesh too more fine than extremely fine. I also added boundary layer mesh (I do not know if this is right to add boundary layer mesh) but the result did not change.
Thank you.
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I have some issues with your 2nd model too, for me Cu should be domains #2+3, and air domain #1
the curent should be defined in #2+3 (perhaps with opposite signs)
The mesh should have a boundary element for the Cu domains and the sub node boundary mesh for the 2x4 segments of the two Cu domain boundaries (the 1/4 circle segments), then you can relax somewhat your extremely fine mesh elsewhere.
Still, once changed, I agree the result looks strange, but I'm afraid that could come from your old version. The v4.0 was not nicely ironed out, you should use a more recent version or the stable 3.5a, there are probably even several bugs left in the early 4.0
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Good luck
Ivar