End Effects in Multiphase Fractional Slot Concentrated-Winding Surface Permanent Magnet Synchronous Machines

Fractional-slot concentrated windings have been gaining a lot of interest in permanent magnet synchronous machines. This is due to the advantages they provide, including shorter nonoverlapping end turns, higher efficiency, higher power density, higher slot fill factor, lower manufacturing cost, better flux-weakening capability resulting in wider constant power versus speed range, and fault tolerance. This paper investigates the end effects in this type of machines. The study focuses on eddy-current losses in the frame, end shields, and clamping rings (magnetic/nonmagnetic). Desirable slot/pole combinations for different number of phases are investigated including both the single- and the double-layer windings. Suggestions for clearances between end windings and the support structure are given.