E. Schmidt:
"Homogenisation of Slotted Geometries in the Finite Element Analysis of Electrical Machines";
Talk: Progress in Electromagnetics Research Symposium (PIERS), Singapore; 01-07-2003 - 01-10-2003; in: "Proceedings of the Progress in Electromagnetics Research Symposium (PIERS)", (2003), ISBN: 0-9679674-0-6; 203.

To enhance the path of the magnetic flux, an electrical machine is
commonly equipped with a slotted stator and rotor. These slotted
geometries are not uniform with respect to the direction of motion.
Nevertheless, the airgap between stator and rotor is invariant along
the motional direction in many applications. Due to an appropriate
distribution of the windings in the slots, also the airgap field is
relatively smooth. Thus, the magnetic flux density in the airgap is
approximately represented by an electromagnetic wave in motional
direction. With this assumption and a simultaneous homogenisation of
the slotted geometries, the transient finite element analysis within
motional simulations can be substantially simplified. In particular,
this is important with the fully coupling of power electronics circuits and the electrical machine in case of analyses for high-performance or high-speed electrical drive applications.