Unequal-Thickness Flat Wire Winding-Based Eddy Current Loss Reduction for Coreless Axial Flux Permanent Magnet Synchronous Machine Adapted to Extended-Range Electric Vehicles

Axial flux machines are increasingly attracting attention due to their power density and compact structure, making them particularly suitable for extended-range electric vehicles (EREVs). Among these, the coreless axial flux permanent magnet synchronous machine (CAFPMSM) with flat wire is renowned for its high copper filling, thermal conductivity, and efficiency. However, the flat wire in CAFPMSM is subject to substantial eddy current losses induced by the magnetic field. To mitigate eddy current loss, an unequal-thickness winding structure with multilayer flat wire is proposed in this article. A mathematical model is first developed to quantify the eddy current losses based on the air-gap flux density distribution. The relationship between the thickness of each layer of the winding and the resulting eddy current loss is analyzed. Second, the proposed winding configuration is further evaluated through 3-D finite element analysis (FEA) to assess its effectiveness in reducing losses. Finally, comprehensive experiments are carried out to demonstrate the effectiveness of the unequal-thickness windings in reducing eddy current loss and improving the efficiency of the machine.