Discussion Forum

Hi

there is one feature one must/should not forget: material are (currently) applied per element type: i.e. you have domain material properties and boundary material properties etc. So if you add a "thin feature on a boundary you must also add (or de-double) a material for this boundary, and specify in the material properties: "Geometrical Entity level: Boundary"

But as you defined the "user property, I believe its not 100% correct that COMSOL should flag a "material omission error"

Then if you want to resolve details (i.e. skin effects) in the coil, you need a mesh fine enough in the material (Cu part) to resolve the gradients, and I would propose that you use boundary mesh elements there too (see the doc)

Then I would start with a 4x or 5x smaller air radius to have a smaller model, you could later add a layer and a spherical infinite layer, to improve the results

i.e. plot a contour line and see if you have at least 1-2 elements per line

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Good luck
Ivar

Dear Ivar,

Thank you for your precious information. As you can see in the new *.mph attached file, i implemented all your aforementioned points, but the "thin low permeability" boundary condition still doesn't have any effect on calculations.
I expect that by defining this boundary the first winding divides into two separate parts so i can see induced currents separately in both parts. But when you look at the current density (phi component) it seems that the software still considers the first winding as a continuous solid winding (please correct me if i am wrong).
Maybe i am using an inappropriate feature to have an "electrical insulation layer" between two solid windings. Let me ask my question in another way and i would really appreciate it if you can help me with my problem:
what do you suggest me to do to model an "electrical insulation layer" which electrically separate a solid winding into two parts?

Thank you in advance,
Warm Regards
Saeed

Hi

indeed not sure why I see no difference with or without your boundary layer (and the suppression of the air boundary definition). One other way to study this behaviour is to add two "layers of i.e.18 mm on your first rectangle (select left and right)

then to model the air as a "true" thin air domain and then to compare the results (mesh the Cu + thin layer as tri before the boundary layer)

But I do not see any major difference there, so I wonder if it is not correct

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Good luck
Ivar

Hi,
I'm facing the same problem as Saeed. I need to model an electical separation layer between conductors, but the "thin low permeability " boundary condution has no effect on results.
I solved the problem by creating a physical thin air layer between the conductors, that of course requires a very fine mesh. But I still don't understand why the original b.c. doesn't wotk.

Regards
Massimo

Hi,

in MEF you can check, if Transition Boundary Condition is working for you.
For frequency domain I have modified your example (MEF is not for transient).

Ralf