Method of starting a permanent-magnet synchronous motor equipped with angular position detector and apparatus for controlling such motor

摘要

An angular position detector for generating trains of A- and B- phase pulses which are 90 out of phase with each other and a C- phase pulse per rotation are mounted on a permanent-magnet synchronous motor such that a magnetic pole origin of permanent magnets and a position where the C-phase pulse is generated agree with each other. After a power supply voltage is applied and in an initial stage before the permanent- magnet synchronous motor is operated normally, a motor control apparatus operates a current control loop with an alternating current command having a constant amplitude and a low frequency to supply an alternating current having a low frequency to the permanent- magnet synchronous motor for thereby rotating the rotor of the permanent- magnet synchronous motor from a stop at a low speed. The motor control apparatus then detects arrival at a magnetic pole reference when a C- phase pulse is detected, and detects an angular displacement of the magnetic poles of the rotor using counts of the A- and B-phase pulses counted in synchronism with the rotation of the rotor after the C-phase pulse is detected.