Review of Electrodynamic Bearings

When Earnshaw stated his theorem in 1839, it did not seem possible to levitate objects in static magnetic fields. 100 years later Braunbeck 1939 was able to show mathematically that levitation is actually possible in unvarying magnetic fields for diamagnetic materials. Today levitating toys based on weakly diamagnetic graphite and permanent magnets are available on the market. Some other materials like superconductors or moving conductors have properties that to a much higher extent resemble those of diamagnets, and these may also levitate in a static magnetic field. Levitating experimental full scale trains based on both of these effects exist today. In this paper the most important technical achievements regarding electrodynamic levitation will be reviewed, dating from 1922 and on, with particular focus on rotating bearings and demonstrated levitating prototypes.