Control of flywheel system with high-Tc superconducting bearings

The high-Tc superconducting levitation system is stable in both radial and axial directions without contacts, so it has been applied as bearings of an energy storage flywheel. To have high efficiency, the rotating speed of the wheel is significantly high, and it is necessary to pass through critical speeds. Rotating tail stocks are often attached at both ends of the shaft, and those are removed after passing through the critical speeds. But the method is complex in practical use. The present article discusses a method for passing through the critical speeds by using magnetic actuators. The analytical results for the system are first obtained, then a control method for the system is presented. Numerical calculations are carried out for a typical problem, and it is ascertained that the present system and control method are applicable to high-Tc superconducting bearings.