New Measurement Approach and Development of 3-D-Printed Core for Yokeless Axial-Flux Machine

Magnetic material characterization for yokeless and segmented armature (YASA) machines poses unique challenges compared to radial flux machines due to their distinct design. In such machine, the magnetic flux paths are different from traditional radial flux machines. This nonconventional geometry complicates the characterization process as traditional methods optimized for radial flux machines may not be directly applicable. This article introduces a new measurement approach for the traditional-manufactured YASA core as well as free-shaped 3-D-printed ones. Today, additive manufacturing (AM) offers more feasible solutions to the manufacturing and assembly of electrical machines with complex 3-D designs, such as axial-flux motors. With particular focus on 3-D printing of magnetic materials, this article discusses the development of AM stator core for YASA axial-flux machines. Aiming to core loss reduction at high frequency, an AM shape-profiled core segment is proposed for a YASA machine. Unlike the conventionally stacked core, the proposed AM core has a better magnetic flux density distribution over its cross section and consequently lower core losses. Moreover, a novel testing approach has been developed and validated for YASA cores. Using AM technology, the printed prototype combines the manufacturing simplicity and high electromagnetic performance merits, allowing for higher power density axial-flux machines. Finally, the performance of a YASA machine is evaluated at a wide speed range considering different core types.