Impact of saturation and inverter cost on interior PM synchronous machine drive optimization

This paper discusses cost-optimized interior permanent-magnet (IPM) synchronous machine drive designs and the impact that magnetic saturation and inverter cost have on their performance and design optimization. Cost-optimized designs for IPM machines and combined machine-inverter systems are compared for an automotive starter/alternator application. The optimization is performed twice, once with a linear lumped parameter model, and again using a nonlinear saturating model. The saturating model produces cost-optimized IPM machines that have lower saliency ratios, larger volumes, and more magnet material than the linear nonsaturating designs, but the saturating model designs are electromagnetically realizable, unlike the linear model designs. The inclusion of inverter cost in the drive cost optimization has a significant impact on the machine design, exchanging a larger and more expensive machine for lower power electronics costs made possible by reduced inverter current.