Design And Analysis Of Fractional-slot Concentrated Winding PM Machines For Electric Vehicle Applications

With the growing energy crisis and environmental pollution, the development of electric vehicles(EVs) is gaining more and more attentions. As one of the key components of electric vehicles, the drive motor determines the main performance of electric vehicles. Compared to other types of machines, the interior permanent magnet(IPM) machines have been the trend of EV traction motors mainly due to their inherent advantages, such as high torque density, high efficiency, wide constant power speed range, high reliability and low noise and vibration. Moreover, machines with fractional-slot concentrated windings(FSCWs) exhibit advantages including short end winding, low Joule losses, cost-effective manufacturing, high fill factor, and fault tolerant capability, and have been widely used in area of servo motor and wind generator. Therefore, it is of practical value to study FSCWs IPM machines for EV applications.Above all, according to the requirements of a drive motor for electric buses, the basic dimensions of a FSCW IPM machine are determined by reasonable selections of pole-slot combinations, electromagnetic load, rotor structure, etc. After that, the size and parameters of the machine are optimized by using field-circuit calculation software and finite element analysis software. Subsequently, a detailed comparison of machines with integral-slot distributed and fractional-slot concentrated windings is presented. The harmonic contents are compared through the analysis of stator magneto motive force(MMF). Then the comparative investigation is carried out based on different design conditions. Key performance metrics are compared and the characteristics of each machine are summarized. Finally, in view of the sub-harmonic effect on the performance of machines with fractional-slot concentrated windings, methods of multilayer windings and spoke-type magnets are investigated respectively, in order to suppress the sub-harmonic component and improve the performance of the FSCWs IPM machines for high speed applications.To conclude, IPM machines with fractional-slot concentrated windings exhibit lower torque ripple and higher the flux-weakening capability, which are particularly suitable for electric vehicles. However, the rich harmonic contents in magneto motive force are harmful to machines' overload capability and cause high rotor losses at high speed. Thisdissertation provides a reference for the application of FSCWs IPM machines in the field of electric vehicles.