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Bearingless Fan                  

ebmpapst St. Georgen GmbH & Co KG and LCM have jointly developed a magnetically levitated fan. The main focus of the development was to enhance the life time of compact high speed fans. At present, the roller bearings used in such fans are the main reason for a limited life time.

The “bearingless fan” has a very high power density which corresponds to a high rate of air flow and it runs, according to the aerodynamic needs, up to 16.300rpm at a power consumption of 30W. The power electronics of the prototype were carried out in an external housing, but the integration within the fan housing is possible. For levitation of the rotor (speed 0 rpm), the whole system consumes only 1,7W.

Bearingless Fan Prototype with Power Electronics

The main challenge in the design process was to achieve a low-cost system with high stability against external disturbances and the unbalance of the rotor. A cost-saving magnetic bearing setup could be achieved through permanent magnetic passive stabilization of all radial and tilt degrees of freedom of the rotor. Only the axial degree of freedom is stabilized by an active magnetic bearing. In order to reach a superior lifetime in harsh environments, special permanent magnets and metal alloys have been used.

Cross Section of the Bearingless Fan

As the passively stabilized degrees of freedom are basically undamped, the stator is supported by viscoelastic damping elements. High vibration resistance is obtained by the optimization of the overall system, taking into account the simulation of the rotordynamic behaviour, the modelling of the frequency- and temperature dependent viscoelastic material as well as the damping effects through eddy currents.
The torque is generated by a sensorless BLDC with 9 slots and 6 poles.

Gerald Jungmayr, JKU
ebmpapst St.Georgen GmbH & Co KG