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A clear trend towards smaller systems saving material cost and weight can be observed in many modern drives. By increasing the speed, equal output power can be provided by a much smaller system. Mechanical bearings often limit the maximum speed and the achievable life time of such drives.

High speed bearingless disk drive with demonstrator impeller
Cross section of selected topology
Speed map of bearingless drives

The Linz Center of Mechatronics GmbH is, therefore, researching the high-speed suitability of bearingless drives with a magnetic bearing integrated into the motor unit. The magnetic levitation allows almost unlimited mechanical lifetime, abrasion- and lubrification-free operation and eliminates friction losses of any contacting parts. An additional benefit is the possibility of hermetically sealing the rotating parts without any sliding parts or sealings. A disk rotor topology with a slotless stator and a toroidally wound, 5-phase winding system has been constructed in order to demonstrate the high-speed suitability of bearingless drives. A special feature of the winding system is that it creates both bearing forces and motor torque with the same set of windings. This allows further integration of the drive and, together with the bearingless disk topology, results in a highly compact drive unit. The prototype has been operated to a high-speed of 115.000rpm.

Complete Prototype System

Research conducted at Johannes Kepler University Linz and the Linz Center of Mechatronics GmbH.

Hubert Mitterhofer, LCM