Position sensorless control of surface mount permanent magnet AC (PMAC) motors at low speeds

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. The coils of the motor are all brought out and it is possible to connect the motor in different configurations. 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. Results are presented to show the effectiveness of the new sensorless scheme