A practical magnetic bearing

Over the past several years magnetic suspension has been emerging from the laboratory and a number of successful engineering prototypes have been constructed both here and abroad. Advances in magnetic materials, primarily Samarium Cobalt, and in electronics across the board for sensing and control, have contributed to the realization of completely non-contacting rotating systems employing magnetic bearings to eliminate the last remaining wearout-prone element. Current efforts are being directed more toward reducing the size, weight, and complexity of these devices to achieve acceptance in flight systems than to demonstrate feasibility. This paper discusses an 8 cm diameter by 3.75 cm bearing which can support more than ten times its own weight and uses only 1% of its payload as part of the magnetic suspension. This design is servoed in two axis and is inherently stable in three other degrees of freedom with full rotational freedom in the desired axis. The unit has capacitive radial position sensors integrally built into the magnetic gap to further simplify its use.