H-Axis Washing Machine Sensorless PM Motor Drive Reference Design Using MC56F80xx

Electronically controlled three-phase permanent magnet motors offer a unique set of features that enhance efficiency and power density. Optimal performance is achieved when the PM motor's excitation is precisely synchronized with the instantaneous rotor position. This means that shaft position information is crucial for successful PM motor control. This application describes a motor control technique for permanent magnet motors (PM motors) that eliminates the need for rotor position sensors. This technique is specifically targeted at belt-driven horizontal-axis (H-axis) washing machines in the low-horsepower range. The PM motor control solution is based on field-oriented control (FOC) and implements a speed control loop. This includes an inner current control loop for excellent torque control performance. To maximize converter efficiency and minimize speed, the current loop is designed using a maximum torque/ampere criterion. Even this sensorless control technique can be implemented on a low-cost 32-MIPS digital signal controller. The application is a single-chip solution based on the DSC56F80XX digital signal controller family.