Fundmental Research On Bearingless Slice Motor

The bearingless slice motor has obvious practical features in high speed applications and ultra-pure field including biology, chemistry, medical industry and semiconductor manufacture because of its integration of both passive and active suspension. A comparative systematical and deep study of the motor is made in the thesis, including mathematical models derivation, structure design, motor control etc.One important feature of the bearingless slice motor is the passive suspension which affects the whole system directly. The magnetic circuit analysis combined with finite element method (FEM) is utilized to deduce the passive force model of Non-PM motor. And the PM motor's passive force characteristic is analyzed by FEM directly. On this basis, the rotor dynamics of the bearingless slice motor is studied to lay a foundation for further study.The bearingless slice motor has a variety of structures, and each type of which has its own feature. To compare different structures, a radial suspension force model of concentrated-winding surface-mounted bearingless PM motor is deduced by magnetic circuit analysis method and verified by FEM. Based on this, 3 typical structures including concentrated-winding surface-mounted motor, distributed- winding surface-mounted motor and distributed-winding consequent-pole motor are compared in order to provide a reference for application selection. Furthermore, to solve the problem that the power of the bearingless slice motor is hard to improve, a double stators scheme is proposed. FEM results show the scheme increases the suspension forces and torques dramatically and decreases the weight of rotor evidently.The concentrated-winding surface-mounted bearingless PM slice motor shows superiority in small and medium power applications. In design aspect of this motor, a point-by-point optimization method of PM shape based on FEM is proposed. By the optimization, a high quality sinusoidal PM magnetic field is obtained to keep radial suspension force steady. In motor control aspect, a decouple control of 2-set windings is realized, and the highest speed reaches 15000rpm. Furthermore, the general radial force model of 1-set winding N teeth motor is derived for fault-tolerant operation. And the stable suspension of 1-set winding motor is achieved by the superposition algorithm and the direct-solving algorithm respectively. On this basis, the fault-tolerant operation of the 6 teeth motor with any one coil broken is implemented.The structure of distributed-winding consequent-pole bearingless PM slice motor is simple, and the motor suits for high power applications. In the thesis, the suspension force pulse of this motor is investigated for the first time by magnetic circuit analysis and FEM validation. The reasons of radial force pulse of different pole number structures are revealed, and the corresponding solutions are presented. Based on this, the suspension pulse is suppressed by proper design, and the 3 pole pairs motor's stable operation is achieved at suspension state. The limitation that the pole pair number of this motor is greater than 3 is broken, and application field of this motor is widened.At last, considering the eddy current displacement sensor applied in bearingless slice motor is hard to decrease cost, two type of hall displacement sensors with both closed and open magnetic circuit are proposed respectively. Magnetic circuit analysis and experiment are processed, and the hall displacement sensor is applied in the bearingless slice motor to reduce the whole system cost successfully. ?...