On-line tracking of the MTPA trajectory in IPM motors via active power measurement

The real-time tracking of the Maximum-Torque-Per-Ampere (MTPA) trajectory in Interior-Permanent-Magnet (IPM) motors is addressed in this paper. The considered approach is based on the injection of proper current test signals and aims at minimizing torque oscillations at the injected frequency, this last condition assuring MTPA operations. Differently from previous approaches motor active power is monitored to detect the out-of-MTPA condition (i.e. torque oscillations), instead of measured motor speed, thus avoiding the use of high-resolution speed transducers, as required by previous approaches. Analytical development are provided, as well as simulation and experimental results, proving the effectiveness of the proposal.