Influence of PM-Material on the Parameter Uncertainty of Bearingless Synchronous Machines

Abstract:
Bearingless machines require an asynchronously rotating stator field wave in order to generate a non-moving force vector which is needed to control the position of the rotor. Such machines are oftentimes built with a solid permanent magnet ring on the rotor surface. Depending on the corresponding frequency and the electrical conductivity, the occurring eddy currents can lead to severe deformation of the exciting stator field wave. This causes a decrease in the force amplitude. Additionally, an error angle occurs between the reference and the actual bearing force vector. PM-materials with sufficiently high electrical conductivity, such as SmCo5, lead to these effects and may endanger robust control.