Back Yoke Design of Axial Flux Permanent Magnet Motors with Fractional-Slot Concentrated Winding for High Power Density

Many researchers have investigated axial flux permanent magnet motors (AFPMMs) with fractional-slot concentrated winding (FSCW) to achieve high power density. For an AFPMM with an FSCW, the path of the magnetic flux is determined based on the winding characteristics and position of the permanent magnet. Therefore, magnetic saturated and non-saturated parts of cores are regularly present. The back yoke of the cores is generally designed only in terms of width because it can control the magnetic saturation. However, designing the back yoke only by width has a limitation in considering the non-saturated part of the cores, which can cause a decrease in power density. Therefore, by modifying the topology of the back yoke to consider the non-saturated part of the cores, the power density can be improved. In this study, we designed the back yoke of a single-sided AFPMM with an FSCW using design variables to increase the power density. Subsequently, by applying the same process, we designed the shape of the back yokes of double-sided type AFPMMs to improve the power density.