2003 Volume 123 Issue 11 Pages 1359-1370
A salient-pole permanent magnet synchronous motor (SP-PMSM) has the high potential for applications requiring energy-efficient and/or wide-speed-range operation. For SP-PMSM, the same torque can be produced by a variety of currents due to nonlinearity between torque and torque-producing current. The appropriate determination of a current command plays a key role to achieve possible energy-efficient and/or wide-speed-range operation. This paper proposes new methods for determining the optimal current command for energy-efficient and wide-speed-range operation of SP-PMSM with core-losses. Proposed methods determine the current command based on a given torque command such that total loss consisting of copper and iron losses can be minimized if the exact solution exists, the best approximate torque can be produced if no exact solution exists. The determined current command is the optimal in sense of energy-efficiency or degree of approximation and can realize wide-speed-range operation. New real-time recursive algorithms searching the optimal current solution for nonlinear simultaneous equations defining optimal current trajectories are also given with convergence verification through experiments. The proposed methods are analytical but practical, and can be applied in both control modes of speed and torque.