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High Torque Density Fractional-Slot Concentrated-Winding Axial-Flux Permanent-Magnet Machine With Modular SMC Stator

In this article, the implementation of a single-stator double-rotor fractional-slot concentrated-winding (FSCW) axial-flux permanent-magnet machine is presented to verify a simple and reliable structure design and oil-immersed cooling of the stator with modular soft magnetic composites (SMC) core. Due to the yokeless and segmented stator, the process of embedding the windings into the stator teeth will probably become simpler. By preforming rectangular copper wire, the shorter end-winding length and higher fill factor can be achieved. In order to eliminate eddy current losses and manufacturing costs, the fiberglass epoxy is used for the supporting components of the fixation for modular SMC stator and PMs, which is a nonmagnetic and nonconductive material. Hence, the robustness of stator and rotor are taken into account due to the stator modularity weakening effect on strength. Meanwhile, a fully sealed stator with oil-immersed cooling is proposed to enable the current density of 20 A/mm2 in the armature windings for stable operation. The electromagnetic properties, including in magnetic field distribution, torque capacity, and flux-weakening ability, are performed based on the three-dimensional finite-element analysis, as well as the mechanical performance. The coupled thermal and computational fluid dynamics model is built to predict the flow and temperature distribution inside stator with oil-immersed forced cooling. The construction and experimental verification of a full-scale 30-kW prototype are elaborated to verify the predicted performances in terms of torque density, structural strength, and cooling.