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### Nodal Forces with permanent magnet

Posted: 23 Apr 2021, 14:36
Hi all,

I'm investigating an electrical machine in 2D with embedded permanent magnets in the rotor.
If I calculate the torque by means of giving "r outer" and r Inner" (Arkkio's equation?) and compare it with the torque calculated by means of "Torque Groups" on the stator, the results are quite similar. However, if I calculate the torque by means of "Torque Groups" on the rotor the results are different (difference around 1%).
In Paraview, I saw nodal forces on several places in the rotor. I didn't understand the nodal forces around the magnets and tried to understand it.

I made a simple example (Magnet3.zip) with an iron circuit (light grey) around a magnet (red).
Magnet3.png (5.85 KiB) Viewed 1175 times
The magnet is magnetized in the x direction and in Paraview (the vtu file is in Magnet3.zip), I saw nodal forces (x component) on the iron sides of the small air gaps between iron and magnet. However, I missed the corresponding force on the magnet side.

Any help in understanding this problem is helpful.

With kind regards,
Martin Hoeijmakers