“True-MTPL” – A New Optimization Method for Minimum Loss Operation of PMSM Drives

The torque produced by a permanent magnet synchronous machine (PMSM) is set by its stator currents. Since a requested torque can be produced by various combinations of stator currents, different strategies like maximum torque per ampere (MTPA) or maximum torque per loss (MTPL) can be applied to determine the current set-point for a requested torque. This work proposes a new strategy for current set-point generation with the objective of maximum efficiency. The new strategy runs an offline-optimization on measured data to find the most efficient current set-points for a given torque request. Compared to conventional MTPL from finite element analysis (FEA), it considers all losses including inverter caused losses and losses due to harmonics of the motor. It is named True-MTPL for this reason. Measurements on a testbench proof its capabilities. Compared to a conven-tional MTPA strategy the losses at high speed and partial load can be reduced significantly.