Robust Angle-Sensorless Control of a PMSM Bearingless Pump

In the semiconductor industry, where bearingless pump systems are employed as the state-of-the-art technology, the trend goes toward higher fluid temperatures (150 degrees C and more) in order to further increase process efficiency. This fact translates into 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 hallsensorless control of a permanent-magnet synchronous machine bearingless pump in its operating range from 0 to 8000 r/min and from zero load to full load. The sensorless operation is performed by the following three novel control functionalities: a controlled startup 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. In particular, 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.