Finite-element performance comparison of IPMSMs with unsymmetrical double-layer windings

This paper presents a comparison of the performances between IPMSMs (Interior Permanent Magnet Synchronous Machine) with a symmetrical and with two different types of unsymmetrical windings. The aim is to demonstrate that the adoption of slightly unsymmetrical windings does not significantly affect the performances of the machines, both in terms of cogging torque and torque/load angle characteristics, providing also the advantage of a higher possibility of choice in terms of slot number/poles ratio. More in particular, an IPMSM model (named IPMSM-1) derived from a commercial geometry equipped with a symmetrical winding is analyzed by using a Finite Element Method (FEM) approach. The simulation results regarding the cogging torque trend, the static characteristics and the related harmonic analysis are shown and discussed. Afterwards, two other IPMSM models with unsymmetrical windings are obtained by modifying the IPMSM-1 stator structure, but maintaining the same rotor configuration. FEM analysis are carried out also for these geometries and the related simulation results are compared with those obtained for the IPMSM-1 model. From this comparison it can be stated that the equipment of slightly unsymmetrical windings can be a viable choice during the design process of rotating electrical machines.