Fundamental Research On Hybrid Magnetic Bearings

The bias magnetic fields of hybrid magnetic bearings (HMBs) are created by permanent magnets so that the power consumption of magnetic bearings can be reduced effectively. HMBs have irreplaceable advantages in those fields that have high demands on power consumption, such as aeronautics and astronautics, energy storage and energy conversion etc. Hybrid magnetic bearing is an important development direction in magnetic bearing technology. This dissertation is footed in the basic characteristics of HMBs and researches on some aspects of HMBs, such as classification system, topological structure, parameter design and optimization, magnetic field analysis and system design.Based on analyzing the basic characteristics of HMBs, the classification of HMBs is studied at first. A classification basis is presened for the first time that HMBs can be distinguished according to their control magnetic fields distribution in air gaps. Combined with the differences in function and bias magnetic fields polar distribution, a novel classification system of HMBs is constructed.Based on the classification system of HMBs, the topological structures of HMBs are studied, and a topological structure design method is presented. According to the type of one hybrid magnetic bearing, the basic topological structure of it can be schemed out. Using this method, the concrete topological structures design of each type of HMBs is studied. Previous topological structures are rearranged and classified, and some novel topological structures are presented. At the same time, the advantages and disadvantages of each topological structure are analyzed and compared qualitatively.Based on the equivalent magnetic circuit method, parameters design method is studied. A design method based on total magnetic flux calculation is presented to improve the optimization degree of parameters. The magnetic reluctance coefficient and magnetic leakage coefficient are obtained by finite element method through cyclic iteration to improve the the design precision.Based on the general parameters design method presented above, the concrete parameters design methods of a hybrid axial magnetic bearing, a hybrid radial magnetic bearing and a hybrid axial-radial magnetic bearing are studied. Based on analyzing the topological structures and magnetic fields distribution, the parameters design and optimization formulas of soft magnetic material components, permanent magnet components and windings are derived. The design goal is maximum bearing force of HMBs, the constraint condition is unsaturated flux density in soft magnetic material and the optimization object is minimum volume. Based on MATLAB, the design and optimization softwares are developed which have a friendly interface and a simple operation. Magnetic fields in HMBs are simulated and analyzed by using finite element analysis software. Parameters design formulas are perfected in reference to the simulation results. Parameters of HMBs are finally obtained which can meet the design goals.Hybrid magnetic bearings system is studied. A five degrees of freedom motor system is built, which consists of a hybrid axial-radial magnetic bearing, a hybrid radail magnetic bearing and a high speed motor. Two hybrid magnetic bearings in this system have similar topological structures and most parts of them can be exchanged. The digital control system and switching power amplifiers of the system are designed. The rotor is suspended stably from 0 to 20000r/min. The parameters design method is proved to have higher accuracy by test data.