Fractional-slot concentrated-windings: A paradigm shift in electrical machines

Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining a lot of interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high power density, high efficiency, short end turns, high slot fill factor especially when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault-tolerance This paper is going to provide an update of the key activities and research trends in this area over the past few years. These include efforts to reduce losses especially rotor losses in FSCW machines, exploring FSCW for machine topologies other than PM machines as well as some of the commercial products that utilize FSCW.