Multi-layer windings effect on interior PM machines for EV applications

This paper mainly studies the effect of the winding layer number on the performance of IPM synchronous machines equipped with fractional-slot concentrated windings (FSCW) for electric vehicle (EV) applications. In order to quantitatively evaluate FSCW-IPM machines with different numbers of winding layers, three models with single-, double- and four-layer winding configurations will be built, comparing back EMF, average torque, torque ripple, core losses, flux-weakening capability, overload capability, etc. It is proved that multilayer windings yield lower d-axes inductance, which leads to weaker flux-weakening capability but better overload capability. It is also shown that torque ripple and core losses are significantly reduced in machines with multilayer windings. Theoretical and finite element analysis have been carried out to verify those conclusions.