Fractional-Slot Concentrated-Winding Axial-Flux Permanent-Magnet Machine With Tooth-Wound Coils

This paper presents the design, finite-element (FE) analyses and experimental validation of a Kaman-type fractional-slot concentrated-winding axial-flux permanent-magnet machine with tooth-wound coils. In this particular topology, the flux travels axially through the permanent magnets, from one stator to the opposite, so that there is no need for any rotor back iron. Thus, the rotor is an assembly of permanent magnets and a suitably designed holder. In order to guarantee adequate mechanical stiffness, stainless steel has been selected as the holder's material. Different designs of this holder are investigated, with the aim of minimizing the induced losses therein. Both no-load and on-load performances are analyzed with 2-D time-stepped FE simulations, with particular attention devoted to rotor losses. A full-scale prototype is built, together with two of the previously investigated holder structures. Experimental tests confirm the validity of the design and of the FE simulations.