Synchronous motor control method and synchronous motor control system

摘要

A desired q-axis current is determined based on a desired torque, and a desired d-axis current is determined based on the rotating speed of a synchronous motor when the terminal voltage of the synchronous motor coincides with a predetermined maximum permissible voltage to weaken a magnetic field created by the synchronous motor equivalently and to prevent the drop of the output torque of the synchronous motor. The desired d-axis current is determined based on the desired torque and the rotating speed. Therefore, the desired d-axis current can be reduced when a high torque is not necessary and undesired increase of the desired d-axis current can be prevented. Thus the synchronous motor operates efficiently, heat generation of the synchronous motor is prevented and power factor is improved.