Electrodynamic magnetic suspension-models, scaling laws, and experimental results

A simple experiment illustrating the principles of electrodynamic magnetic suspension is described and test results are given. A disk-shaped coil made of insulated copper magnet wire and energized with 60-Hz ac line voltage is levitated in a stable equilibrium position above a wide aluminum plate. The mechanisms generating levitation force are identified by the use of Maxwell’s equations. A lumped-parameter inductance model is used to model magnetic energy storage. By using energy methods, the current necessary to achieve coil lift-off and levitation is estimated, with good results. A stability analysis is done which shows that the levitation is stable, but underdamped. Thermal models are also developed for determining temperature rise in the coil. The magnetic scaling law is developed which shows that larger magnetic structures are more efficient in energy conversion than small ones.