Design, Analysis and Comparison of 5kW Synchronous Reluctance Motor and Interior PM Synchronous Motor for EV Application

This paper presents the design and comparative analysis of a Synchronous Reluctance Motor (SynRM) and an Interior Permanent Magnet Synchronous Motor (IPMSM) for electric vehicle applications. The primary objective is to evaluate the feasibility of SynRM, a rare-earth-magnet-free motor, as a viable alternative to PM-based motors. A 5 kW, 3000 RPM IPMSM is used as a reference design, providing the benchmark for developing two SynRM variants for equivalent power and torque ratings. A comprehensive analysis is conducted at both rated and peak operating points, comparing flux densities and electromagnetic performance of the motor. The study reveals that due to the lack of rotor excitation in SynRM, achieving comparable performance requires trade-offs in current density or motor size. To match the peak torque of the IPMSM within the same frame size, significantly higher current densities are necessary for the SynRM, primarily due to core saturation effects. Further, the influence of current magnitude and current angle on the saliency ratio and inductances of the SynRM is also examined. Finally, the Finite Element Analysis (FEA) and Maximum Torque per Ampere (MTPA) characteristic of the SynRM variant with 30% higher motor volume is presented compared to the IPMSM. The results show that SynRM achieves the desired rated performance, i.e., rated torque of 16.8 Nm with a torque ripple of 8% at 2982 RPM and efficiency of 91.7%.