Robust sensorless control of a PMSM bearingless pump

Abstract

In semiconductor industry, where bearingless pump systems are employed already as state-of-the-art technology, the trend goes towards higher fluid temperatures (150degC and more) in order to further increase process efficiency. This fact translates to the requirement of a high.temperature bearingless pump system and/or the elimination of thermal-critical components such as hall sensors. This paper introduces a new method for a hall-sensorless control of a PMSM bearingless pump in its operating range from 0 rpm to 8000 rpm and from zero load to full load. The sensorless operation is performed by three novel control functionalities, namely: a controlled start-up routine, enabling a sure levitation and zero angle setting; an open-loop angle estimation based on stator voltage and stator current measurement and known machine parameters; and an angle synchronization establishing a robust operation of the pump in the whole operating range even for a large machine parameter drift. Especially, considering the temperature degrading of the permanent magnet flux density, the novel robust control concept is of great benefit for bearingless pump systems employed in high temperature applications.