Comparative Study of Multiphase IPMSMs for EV Applications

Three-phase, five-phase, dual three-phase, and nine-phase interior permanent magnet synchronous machines (IPMSMs) are optimized using the same structural parameters of the reference Tesla Model 3 IPMSM for electric vehicles. The optimized three-phase machine shows 20% higher torque per permanent magnet volume compared to the reference design by optimizing the machine structure. It is shown that the multiphase machines offer higher average output torque and higher efficiency while using less amount of permanent magnets. Moreover, the torque ripples of the multiphase machine are found to be inherently low even though no skewing or other core shaping techniques are employed. The torque-speed analyses of the multiphase machines demonstrate enhanced efficiency regions attributable to the increased output power although this improvement is accompanied with increased iron losses due to high winding factors of harmonics.