The Study On The Hybrid High-Temperature Superconducting Magnetic Bearing System

The magnetic bearing is a novel type and high performance bearing, which suspend the rotor by magnetic force without any mechanic contact between stator and rotor. One of the most hopeful application fields of high temperature superconductor (HTS)YBCO is superconducting magnetic bearing(SMB). A stable magnetic force exists between HTS bulk and permanent magnet due to Meissner effect (diamagnetism) and flux pinning effect which will generate when HTS bulk transforms into superconducting state. So, a stable levitation can be obtained without using any external control.A new scheme of a vertical hybrid superconducting magnetic bearing including superconducting magnetic bearing, active magnetic bearing, and permanent magnetic bearing has been advanced in this design. The HTS bulk can supply a stable levitation force, an active axial magnetic bearing which is composed by superconducting coil is employed to supply a controlling force. In addition, two radials permanent magnetic bearings are applied to improve the magnitude of radial stiffness and damping of the rotor. The study on the hybrid superconducting magnetic bearings could be meaningful both theoretically and practically.Based on the principles of superconducting magnetic bearings, active magnetic bearing, and permanent magnetic bearing, a new-type five-degree hybrid HTS magnetic bearing experimental device has been built. The properties of high temperature superconducting magnetic bearings are discussed in detail. In this thesis, the magnetization model based on Bean's critical state model is applied to do finite element analysis of the levitation forces and magnetic fields of a superconducting bearing. The principle verification device of the new-type hybrid HTS magnetic bearing have been measured and analyzed.The mathematical model and control method of the one-degree hybrid active magnetic bearing are investigated. The digital controller based on PID method is studied, and the method which is used to design and set the controlling system parameters is discussed. A set of control system for active magnetic bearing including hardware electric circuits and software programs is designed, and the DSP chip TMS320LF2407A controller is taken as the centre of it. The levitation property of the permanent magnetic bearing which is composed by permanent magnet rings with radial magnetization is studied, and its magnetic field distribution and levitation force have been calculated and analyzed by mean of finite element method.The experiment results indicate that the new-type hybrid HTS magnetic bearing can make the main shaft suspend steadily. The superconducting coil which is used to adjust the work gap is helpful for improving the levitation stability, and it can decrease the energy losses and increase the load capacity synchronously. The new-type hybrid HTS magnetic bearing lays a foundation of realizing the high speed rotation sulteriorly.