飞轮电池不对称励磁卸载轴向悬浮混合磁轴承设计

Design of axially suspended hybrid magnetic bearing with asymmetric excitation and unloading for flywheel battery

针对飞轮电池支承与传动系统集成度低、能量损耗大等问题,该文设计了一种兼顾卸载和轴向悬浮的不对称励磁混合磁轴承,该磁轴承拓扑结构由含永磁环的上定子、下定子及转子组成。分析了不同工作模式下的运行机理;综合考虑永磁退磁、最大偏心以及轴向扰动等因素对磁轴承卸载能力的影响,制定了磁轴承额定卸载力约束准则;结合永磁材料工作曲线,推导出卸载力数值模型以及退磁/最大偏心下轴向补偿力数值模型并实现了磁轴承关键结构参数设计。三维有限元分析表明,正常卸载力、退磁卸载力、偏心卸载力的有限元分析值与理论值误差分别为4%、3.7%和5.8%,验证了参数设计结果的准确性。样机试验结果表明,卸载力理论计算值与实测值的最大误差约为4%,平均误差为2%;轴向负载80 N时,转子由上定子气隙处保护磁轴承起浮,稳定悬浮后轴向单边位移约为25μm,轴向负载120 N时,转子由下定子气隙处保护磁轴承起浮,稳定悬浮后轴向单边位移约为35μm,所设计的磁轴承具有良好的卸载与悬浮性能。研究结果可为高集成、低损耗、高可靠性的飞轮电池系统设计提拱参考。

Bearingless flywheel battery has many advantages,such as high specific power,high specific energy,high current receiving capacity(recharge and regenerative braking),long service life,fast charge and discharge,and it is considered to be the most competitive auxiliary batteries for electric vehicle.However,there are some problems in bearingless flywheel motors and some magnetic bearings in bearingless flywheel battery systems,such as low integration,large energy loss and low reliability.Aiming at above problems,an axially suspended hybrid magnetic bearing with asymmetric excitation and unloading which consists a lower stator,a upper stator with permanent magnet ring and a rotor is proposed in this paper.First of all,the mechanical structure of the axially suspended hybrid magnetic bearing with asymmetric excitation and unloading is introduced,and the different operating mechanisms under the conditions of unloading,demagnetization,down disturbance and upward disturbance are discussed.The design criteria is set according to the operating mechanisms under different working conditions.According to the design criteria and the working curve of rare earth permanent magnet materials,the numerical model of unloading force and the axial compensation under demagnetization/maximum eccentricity are deduced.Then,the structural parameters of upper stator and permanent magnet are designed,and the windings of the upper stator and lower stator are calculated considering the constraint conditions of demagnetization and eccentricity.Based on this,three-dimensional finite element model is established.Simulation results show that the flux density is about 0.605 T between upper stator and air gap under unloading mode which verifies the validity of the design method for permanent magnet and upper stator parameters.The suspension force of finite analysis is about 100 N and the relative error with theoretical suspension force value(104 N)is 4%.When working under the demagnetization mode,the flux density is about 0.53 T between upper stator and air gap which approximately equals to the theoretical value(0.54 T).The suspension force of finite analysis is about 78 N and the relative error with the theoretical suspension force value(81N)is 3.7%.When the maximum downward eccentricity is 0.2 mm,the flux density is 0.515 T which approximately equals to the 0.5 T of theoretical value,the suspension force of finite analysis is about 65 N and the relative error with the theoretical suspension force value(69 N)is 5.8%.When the maximum upward eccentricity is 0.2 mm,the flux density is 0.65 T and the suspension force of finite analysis is about 110 N.Finally,in order to further verify the correctness of theoretical analysis,a prototype is manufactured according to the design results.The results of prototype test show that the maximum error between theoretical calculation value and measured value of unloading force is about 4%,and the average error is 2%,the rotor radial displacement is about 25μm when the axial load is 80 N,the rotor radial displacement is about 35μm when the axial load is 120 N.The results indicate the proposed magnetic bearing has a good unloading and suspension performance of the magnetic bearing,which provides a new idea and method for the design of high integration,low loss and high reliability flywheel battery system.