Design of a highly reliable fan with magnetic bearings

Abstract

Bearing failures are, according to long-term analyses at ebm-papst St. Georgen GmbH & Co. KG, responsible for 90% of all compact fan breakdowns. The working life of a fan can be increased considerably by using a magnetically levitated fan, where the impeller has no contact with the stator. This paper presents the design of a low-cost magnetically levitated fan with passive magnetic bearings (PMBs) to stabilise radial and tilt deflections of the rotor. The application of an optimised viscoelastic support to the stator introduces sufficient damping to the passively stabilised degrees of freedom. The optimisation of the stiffness and damping and the design of the key components, namely the PMB, the active magnetic bearing and the passive damping device is discussed. Finally, the built prototype is presented and the measurement results are analysed.