Magnetic-pole detecting system for synchronous ac motor and magnetic-pole detecting method therefor

Abstract

A magnetic-pole detecting system for synchronous AC motors and a magnetic-pole detecting method therefor are provided. The magnetic-pole detecting system for synchronous AC motors includes a position detectorfor detecting the relative position between the moving elementand the stator of an AC motor; a phase-update command unitfor making a plurality of currents with different phases flow in coilsandso that the moving elementmoves to a plurality of stable points; a reversal command unitfor making currents flow in the coilsandso that the moving elementreverses from the previous direction in which the moving elementhas been moved by the phase-update command unit; a current cut-off command unitfor cutting off the currents flowing in the coilsandwhen the position-detectordetects a movement of the moving element; a reversal-determining unitfor determining, based on a position-detecting signal from the position-detector, a direction in which the moving element has moved based on the phase-update command unit, and for determining that the determined direction has reversed between the previous and the present instances; and a stable-point-simulator for simulating a stable point by means of the phase of the currents flowing in the moving elementwhen the reversal-determining unithas detected the reversal.