Influence of wedge material on losses of a traction motor with tooth-coil windings

Permanent magnet (PM) machines with tooth-coil windings are designed and analyzed. We study how the slot wedge material affects the behaviour of losses when using tooth-coil windings. The losses of an interior permanent magnet rotor are studied over a wide speed range. 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 materials are used. The study shows that tooth-coil windings may benefit from using a semi-magnetic material as a wedge material as it decreases the rotor iron losses and, especially, losses in the permanent magnets. The study shows also that wedges with relative permeabilities higher than 3 would not benefit this traction motor design, because of high losses and low maximum torque. Computations are compared to measurements of a 110 kW prototype traction motor.