Influence of slot wedge material on permanent magnet losses in a traction motor with tooth coil windings

Abstract

Permanent magnet (PM) machines with tooth coil windings are designed and analyzed. We study how the slot wedge material affects the behavior of PM losses when using tooth coil windings, which generate a significant air gap flux density harmonic content. The losses and cogging torques of a surface permanent magnet rotor and an interior permanent magnet rotor are compared in no-load and load situations. A finite element analysis applying Cedrat's Flux2D is made. Motors of this size can have high permanent magnet eddy current losses, and therefore, segmented magnets are often preferred even though interior magnets and semi-magnetic wedge material are used. The study shows that tooth coil windings may benefit from using semi magnetic material as a wedge material as it decreases the stator iron losses and, especially, losses in the permanent magnets.