Sensorless Direct Flux and Torque Control for Direct Drive washing machine applications

The paper deals with a Direct Flux and Torque Control (DFTC) scheme for motion sensorless Direct Drive (DD) washing machine applications employing Surface Mount (SM) Permanent Magnet (PM) motors. This solution provides very good performance under current and voltage limitations and represents a viable alternative for washing machine applications. Complete experimental results, obtained on a DD washer prototype, are presented to demonstrate the feasibility of the proposed solution.

I. Introduction

Three-phase Induction Motors (IM) with tachometer feedback and SMPM motors with Hall sensor feedback are two most employed solutions by the washers available today on the North American market [1], while on the European market the washers still employ the universal motor. The mechanical power generated by the motor can be transmitted to the drum using a belt and a pulley. The ratio between the motor speed and the drum speed is from 8:1 to 13:1, allowing using low torque/high speed motors having a low pole-pairs number. Another solution is to connect directly the rotor to the washer drum, obtaining the Direct-Drive (DD) configuration that requires high torque/low speed motors having a large pole-pairs number. The DD solution is more compact, more reliable and allows obtaining a very silent operation for the entire speed range. While the IM is currently employed for belt-driven washers, the DD solution usually employs fractional-slot SMPM motors [2] with internal stator and outer rotor that is connected with the drum.