The Study And Experiment On The Hybrid High-Temperature Superconducting Magnetic Bearing System～2

The magnetic bearing is a novel type, high performance bearing, which suspend the rotor by magnetic force without any mechanical contact between rotor and stator. 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, an axial permanent magnetic bearing is applied to levitate the weight of the rotor, the superconducting magnetic bearing can achieve stable levitation. In addition, two radial active magnetic bearings are employed 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, the motion equation of the five-degree hybrid superconducting magnetic bearings has been built, a five-degree experimental device including a set of control system for active magnetic bearing has been built.The properties of high temperature superconducting magnetic bearings are discussed in detail. In this thesis, the magnetization model based on Bean抯 critical state model is applied to do finite element analysis of the levitation forces andmagnetic fields. The static and dynamic performances of the superconducting magnetic bearing have been analyzed and measured.The control system of active magnetic bearings is investigated. Decentralized control method is used to control active magnetic bearings. The analog PD and PID controller are studied. The application of LQR optimal control theory on the controller design is discussed, and PID with nonlinear regulator has been applied to control the system with high system stiffness and large stable regions.The properties of different permanent magnetic bearings with both axial and radial magnetization are studied by mean of equivalent current and finite element method respectively. The levitation forces and stiffness have been calculated and agreed well with measured data.The static and dynamic characteristics are measured and analyzed, the hybrid superconducting magnetic bearing system can run safely at high speeds up to 9,6000rpm, with large scope stability, which reach the performance object of the initial design.