Design of a Printed Circuit Board Axial Flux Permanent Magnet Machine for High Speed Applications

Recently, printed circuit board (PCB) stators have been proposed for coreless axial flux permanent magnet machines to reduce manufacturing costs and eliminate some of the drawbacks of traditional Litz-wire-based stators. However, their design presents significant challenges. Firstly, the PCB copper traces are exposed to the rotating air-gap field, which causes significant high-speed AC losses. Secondly, standard PCBs hardly satisfy stator winding requirements since the achievable copper fill factor is rather limited. In order to address these issues, the paper proposes a bespoke machine design methodology which relies on original closed-form expressions for eddy and circulating current losses. Additionally, the most recent PCB technological developments are considered in the determination of manufacturing constraints. A case study is provided for a 1 kW, 7500 rpm machine to validate the design method. An original winding layout is proposed to suppress circulating losses. Finally, an extensive set of experimental tests on a full-scale prototype is reported.