Abstract
Recently superconducting magnetic bearings have been applied to many engineering products, such as flywheels and turbo-chargers. This is due to the fact that such bearings, unlike other bearings, can support rotating rotors without any contacts, and make it possible to rotate a rotor up to an extremely high rotational speed. When superconduction bulk material is used as a bearing, it traps a magnetic field received from a permanent magnet, and restoring force acts to return it to the initial cooling position. We considered a case in which the permanent magnet has asymmetry in the circumference direction. Their system is hardly able to be constructed completely symmetric in the circumference direction, and anisotropy can occur in the magnetic field. Equations of the motion that assumed the anisotropy of the magnetic field are derived. We then investigated the behavior of the system numerically, and confirmed that the system has the characteristic of a bearing which has anisotropic restoring force, a flat axle, and the nonlinearity of the restoring force at the same time. According to these effects, the frequency band showing instability of the rotor can be changed.
