An optimal motor drive current model and its application to reluctance motor

Based on the analysis of the motor parameters, an optimal drive current model of synchronous motor is derived with constrained optimal analysis. The results show that, if the inductances of the synchronous motor can be obtained accurately in the space domain, optimal current can be obtained which generates the required electromagnetic torque with minimum copper loss. Analysis elucidates the influence of the high order inductance harmonics to the torque ripple and the waveform of the optimal current. These harmonics cause the optimal drive current to be non-sinusoidal. However, the analysis proves that, in the idealized state, the optimal current is sinusoidal, and the optimal phase angle is determined by the motor inductances. The application of the model to reluctance motor is presented in the paper, and the results confirm the effectiveness of the presented current model and analysis method.

I. Introduction

In this paper, the optimal drive current of synchronous motor is defined as the current which can generate the required constant electromagnetic (EM) torque with minimum copper loss. In the analysis, the motor parameters are independent to the drive currents.