Passive axial stabilization of a magnetic radial bearing by superconductors

Contactless bearings for high-speed operation can be constructed using passive magnet systems which inherently need a second active bearing for their stabilization. Completely passive bearings only can be obtained using diamagnetic materials. The axial stabilization of magnetic radial bearings using a permanent magnet/superconductor system is considered. Using finite-element calculations, it is shown that axial forces of up to 3000 N and stiffnesses of up to 400 N/mm can be achieved; good diamagnetic behavior (μ_r<10^-3) of the superconductor is assumed. It remains to be clarified whether a `real´ superconductor allows reliable bearing operation and whether flux penetration and motion lead to degradation of bearing characteristics during operation