@oscarcorripio, thanks for providing that example. It’s a very good demonstration of how rotating zones should be set up.
Just to add here:
With the MRF approach, instead of “moving” the mesh which would create a high computational effort, we directly add the rotation of the air.
The MRF zone should be placed in the middle between the rotor and stator and it simply has to cover all the rotating parts - thus a close fit around the geometry is fine. It is recomended for it to be axial symmetric- for AMI it is a must, for MRF it is recommended