simulation - COMSOL coil group which crosses the modeling plane more than once

Question

I'm trying to model a system in the magnetic field, 2D-axisymmetric environment, with current loops which pass the modeling place both once and more than once.

I've read here that the solution should be to mark the coils which pass through the plane more than once as a group, but for me it doesn't seem to work. From what I see, it appears that the coils which cross the plane twice (on the right-hand side) are not modelled properly.

All coils are a homogenised multi-group, if that matters.

I'm attaching a 3D model of my setup (with the brown representing the coils, grey the iron core, and the ), and also COMSOL's steady-state results.

I've tried playing around with other parameters such as increasing current and number of coil turns, but didn't see much effect.

Any help is much appreciated.

question from:https://stackoverflow.com/questions/65848120/comsol-coil-group-which-crosses-the-modeling-plane-more-than-once

Answer 1

I played around a bit more, and have figured out a workaround, even though I'm sure there's a more "elegant" solution out there.

Considering that the coil on the right hand side has current entering from one of the cross-sections, and exiting from the other one, one can just treat the coils as individual coils, each with +I and -I current flowing through them.

That is, don't use the "coil group" selection, but rather treat each cross-section of the coil as an individual coil. Just make sure to keep an eye on the polarity of this solenoid i.e. which cross-section has positive current flowing through it and which has negative.

The image below shows the desired result.