End effects in multi-phase fractional-slot concentrated-winding surface Permanent Magnet synchronous machines

Fractional-slot concentrated-windings (FSCW) have been gaining a lot of interest in Permanent Magnet (PM) synchronous machines. This is due to the advantages they provide including shorter non-overlapping end turns, higher efficiency, higher power density, higher slot fill factor, lower manufacturing cost, better flux-weakening capability resulting in wider constant power vs. 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.