Winding Losses in Coreless Axial Flux PM Machines with Wave and Spiral PCB Stator Topologies

Printed circuit board (PCB) stators in coreless axial flux permanent magnet (AFPM) machines have been proposed, designed and studied for utilization in multiple industries due to their design flexibility and reduction of manufacturing costs, volume, and weight compared to conventional stators. This paper investigated loss mechanisms and multiple methods of approximating winding supplementary losses in PCB stators with example wave and spiral winding topologies for a dual rotor, single stator configuration using 3D FEA models with a 15 hour runtime. The effect of rotor magnet placement, end windings, and active conductor path on eddy current is studied for both topologies. A hybrid FEA/analytical approach is proposed for the approximation of circulating current within layers of a planar PCB conductor using the equivalent circuit model. A coreless AFPM motor prototype is created and its power losses tested using multiple PCB stators with the findings being comparable to hybrid analytical methods results.