Analysis and Optimization of Winding Losses of Axial Flux Permanent Magnet Machine with Concentrated Winding Flat Wires

Yokeless and Segmented Armature (YASA) axial flux permanent magnet (AFPM) motors have been found as the highest power density candidate for various axial flux topologies, especially with concentrated winding flat wires. However, this winding configuration produces AC losses that limit efficiency gains. This article primarily discusses the AC eddy current losses calculation of flat wire armature winding and efficiency optimization by matching a perfect tradeoff of AC and DC winding losses by selecting cross profile specifications of flat wire, as well as the axial size of coils distance from the air-gap side. A hybrid analytical– finite element analysis (FEA) method for rapidly calculating eddy current losses of the rectangular cross-section wires is induced and applied for the YASA AFPM motor based on the tangential and axial flux leakage distribution in slots. The specification of flat wire directly affects the AC and DC losses of the windings. Certainly, the axial position of the coil affecting the eddy current loss is also considered. According to the study, two winding structures that can effectively reduce eddy current losses are acquired and the results are also verified. The calculation of winding losses and optimization of flat wire specifications are implemented and validated on the studied 12-slot 10-pole YASA AFPM motor, rated at 35 kW, with open slots by measuring efficiency. Meanwhile, the accuracy of 3-D FEA is further verified.