Discussion Forum

Hey,

i am new to comsol. My task is to model the force of a (planar) multi-turn coil on a disc shaped permanent magnet which is situated with its symmetry axis colinear to the coil symmetry axis at some distance above the coil. The problem is 2D axisymmetric.

For modeling, i
- use comsol 5.2
- used the mf module
- added an amperes law for the permanent magnet with magnetization
- added a multi-turn coil node

Now, i got some issues with the multi-turn coil (mtc) settings:
I selected a rectangular domain for the mtc-feature. I assume the mtc-node splits this cross sectional rectangular area into round wires. The number of wires is determined by N and the cross section of each wire by "a_coil".

However, here is the problem:
Lets say the rectangle i chose has a cross sectional area of A_r.
What happens for instance if i enter a pair of N and a_coil that will be larger than A_r in total:
N*a_coil > A_r. Does it just fill the rectangle with as many wires as possible?
That does not make sense to me.

I tried to find out what effect varying the a_coil parameter has on the z-em-force in the symmetry axis of the magnet, and, surprisingly, the plot shows a constant line (that cannot be true, right??). So i guess there is something i did wrong.

Also i was wondering, is it possible to model the cross section of the wires as rectangles?
My idea would be to use the coil group check box and draw multiple rectangles and select those domains as the windings. But then it would be a pain in the ass to vary the coil windings.

Thanks for your help.

Jan