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

This paper presents the design, finite-element analysis (FEA), and experimental verification of a single-stator double-rotor fractional-slot concentrated-winding axial-flux permanent-magnet machine with core-wound coils. The advantages that are obtained by adopting such coil construction in terms of shorter end-winding connections higher fill factor, and mechanical robustness of the magnetic structure are highlighted. Machine performances both at no load and at rated load are analyzed through static FEA, and a simple index is introduced to compare induced losses in the permanent magnets for various machine configurations. Time-stepped transient FEA is used to validate the index. The construction and experimental testing of a full-scale prototype is described to confirm the expected performances and to characterize the prototype in terms of losses (both at no-load and in loaded conditions), cogging torque, and main machine parameters.