Investigation of Rotor Topologies for Reducing Torque Ripple in Double-Layer IPMSMs for Automotive Applications

Abstract

Interior permanent magnet synchronous motors (IPMSMs) are currently widely used for traction applications. However, the torque ripple in these motors needs to be reduced because it causes vibration and acoustic noise. Accordingly, this study first determined the guidelines for reducing the torque ripple of multilayer IPMSMs and then proposed a double-layer IPMSM with holes drilled in the rotor core. The torque ripple reduction for the proposed rotor structure was examined using two-dimensional finite element analysis and experiments with prototypes. The analytical results showed that, under maximum torque-per-ampere control, the torque ripple using the proposed model was suppressed by 54.8% compared with the reference model while limiting the average torque reduction to 3.6%. Moreover, multi-objective optimization based on the guidelines was performed. With the proposed structure, the torque characteristics at high and low currents were highly correlated, and a similar torque ripple reduction effect was obtained even at low current, which is frequently used in traction motors for automotive applications. Finally, optimization was performed for an IPMSM with other topologies, resulting in verification of the generalizability of the proposed method.