Magnetic Bearing

A magnetic bearing is a bearing that supports a load using magnetic levitation. Magnetic bearings support moving machinery without physical contact. For instance, they are able to levitate a rotating shaft and permit relative motion with very low friction and no mechanical wear. Magnetic bearings support the highest speeds of any kind of bearing and have no known maximum relative speed

Magnetic bearings are difficult to design using permanent magnets due to the limitations described by Earnshaw's theorem while techniques using diamagnetic materials are relatively undeveloped. As a result, most magnetic bearings require continuous power input and an active control syste.m to hold the load stable. Magnetic bearings often use permanent magnets to carry the static load, while a power input is only used when the levitated object deviates from its optimum position. Magnetic bearings typically require a back-up bearing in the case of power or control system failure and during initial start-up conditions.

Magnetic bearings are used in several industrial applications such as electrical power generation, petroleum refinement, machine tool operation, and natural gas pipelines. They are also used in the Zippe-type centrifuge used for uranium enrichment. Magnetic bearings are used in turbomolecular pumps, where oil-lubricated bearings would be a source of contamination.