Method of controlling speed of synchronous motor, and method of identifying constant of synchronous motor

摘要

In sensorless vector control performed through use of a rotation speed of a synchronous motor 6 and the position of a rotor, a positive current is caused to flow to a gamma axis on the assumption that a "d" axis serving as a true magnetic axis is out of phase with the gamma axis by only an angle of load thetae, whereby torque which is proportional to igamma sin thetae and directed toward the gamma axis arises in the magnetic axis. Accordingly, a deviation between a d-q axis serving as a true magnetic axis and a gamma-delta axis serving as a control axis is eliminated. Even if load is exerted on the motor, the gamma axis serving as a control axis is constantly aligned with the "d" axis serving as the magnetic axis of the synchronous motor, thereby enabling excellent vector control.