Piecewise Affine Maximum Torque per Ampere for the Wound Rotor Synchronous Machine

Power-efficient torque control of the Wound Rotor Synchronous Machine (WRSM) requires a minimization of electrical losses, namely copper and iron losses. In this paper, the Minimum Power Loss per Torque (MPLPT) optimization problem is presented and solved using a convex pareto frontier of simulated or measured data points. Magnetic saturation and cross-saturation effects are captured using sampled points throughout full-machine operation. A filtered solution set is mapped to current space using piecewise affine functions, which approximate the current using a piecewise linear function for a given torque. This set of piecewise linear functions enables a machine controller to implement MPLPT online or as an offline lookup table. Results are presented for a 65 kW, FEA-sampled WRSM.