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 (FSCW) axial-flux permanent magnet (AFPM) 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, in order to compare induced losses in the permanent magnets for various machine configurations. The construction and experimental testing of a full scale prototype is described, in order to confirm the expected performances and to characterize the prototype in terms of losses, cogging torque and main machine parameters.