Structural Investigations on Yokeless Electrically-Excited Segmented Armature Axial Flux Motor

To address the environmental, economic, and scalability concerns related to conventional permanent magnet axial-flux machines, the Yokeless Electrically-Excited Segmented Armature (YEESMA) topology has been proposed as a sustainable, high-performance solution. YEESMA eliminates the need for rare-earth magnets, using field windings hosted in rotor slots. However, structural challenges arise due to the unique rotor design, requiring in-depth mechanical analysis to ensure operational reliability at high speeds. This study presents a comprehensive structural assessment of the YEESMA rotors, with a focus on deformation patterns, stress distribution, and overall mechanical performance under centrifugal loads. A detailed Finite Element Analysis (FEA) is conducted to evaluate critical aspects such as radial expansion and stress concentrations at slot fillets. The results reveal that without design refinements, stress levels in key regions exceed material yield limits, necessitating optimization strategies. Two primary design improvements are proposed to enhance structural integrity: increasing slot fillet radii and including containment rings at the rotor slot openings. The study demonstrates that an optimal balance between these design parameters is essential to meet both mechanical and electromagnetic performance. These findings can help with the future development of axial flux machines in e-mobility applications.