Calculation of electric current

Mods FEM
1

Hi,
I would like to calculate the electric current through a surface. I am using the electrostatic equation in Elmer solver with a simple model and constraint electrostatic potential on two opposite faces. The results give me the potential distribution and the electric flux or electric field.

However, these values only take into account the geometry and boundary conditions but not the material properties (electrical conductivity). How to calculate current or current density distribution?

potential_distribution.png
electric_flux.png

OS: Windows 11 build 22621
Word size of FreeCAD: 64-bit
Version: 0.21.0.33668 +7 (Git)
Build type: Release
Branch: (HEAD detached at 0.21)
Hash: 41b058e2087de60dc8fef3d3e68c7d0129e13abf
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: English/United Kingdom (en_GB)
2

I’m definitely not an expert in electromagnetic simulations (my domain is mechanics) but I’m pretty sure that you need more than electrostatics (which deals with electric fields generated by stationary currents). Your problem likely needs a current conduction solver, available in Elmer but not yet implemented in FreeCAD FEM.

3

Thank you for the answer!
Yes, you are correct, I need the Static Current Conduction solver. As you said, it is not implemented in the official source code yet, but I came across this topic:
https://devtalk.freecad.org/t/elmer-static-current-equation/42827/1
and it seems that there are some forks from the official source that already include it. Do you know guys some quite recent unofficial FC builds where the solver is implemented?

4

I don’t think you can find such builds but let’s ask HoWil.

It might be best to just prepare the analysis in Elmer GUI or do the initial setup in FreeCAD FEM, then export the solver input files and edit them manually.

5

Yes, this is my workflow at the moment:
FreeCAD → STEP file model → ElmerGUI → VTU file → ParaView/ElmerVTK

It works fine but I need to do some series of analyses with slight changes in geometry, and having both steps under FreeCAD would allow easier automatization of the whole routine.

6

No, there are no builds from my side.

@uwestoehr: Uwe, since I am too long away and I currently have no time to dig into it, how much work do you think is it to transfer/rebase the old code for the current solver/equation?