Sensorless operation of surface mount permanent magnet AC (PMAC) motors

Abstract

A position sensorless field oriented control scheme for surface mount permanent magnet AC (PMAC) motor is presented. A digital signal processor (DSP) is used to implement the sensorless scheme. The PMAC stator is wound like that of a conventional three-phase induction motor. Taps are also provided which are used for voltage measurements. By measuring the tap voltages, absolute position of the permanent magnet AC motor, driven by a current regulated PWM inverter, with a fixed frequency ramp comparison controller, is estimated. The estimated position information is independent of the stator resistance, thus this scheme is even applicable at low speeds.