Comparison of Direct-Drive Permanent-Magnet Synchronous Motor and Permanent-Magnet Flux-Modulated Motor for Electric Vehicles

Direct-drive in-wheel motors have become an extremely attractive option for electric vehicles. Two kinds of motors are devised, Permanent Magnet Synchronous Motor (PMSM) and Permanent-Magnet Flux-Modulated Motor (PMFM), respectively. Keeping the same back EMF, current density and copper loss, this paper analyzes and compares torque density, torque ripple, flux-weakening performance, speed range, loss and efficiency of the motors. The results indicate that compared to PMSM, PMFM has higher torque density, lower material cost and wider speed range, but with the penalty of lower efficiency, lower power factor and higher iron loss.