考虑部分通道故障的磁轴承系统动态承载力分析

Dynamic Capacity Analysis of Active Magnetic Bearing System with Partial Channel Failure

通道故障后,磁轴承系统的动态承载力将发生变化,该文建立了考虑部分通道故障的磁轴承系统模型以分析该变化。首先以单自由度模型为例,分析由转子位移及通道电流计算系统动态承载力的方法。其次建立考虑动载荷、转子不平衡量以及故障通道电磁力变化的四自由度系统模型,并将单自由度系统承载力分析方法应用于该系统模型,从而得到四自由度系统动态承载力。然后分析通道故障后控制参数对系统动态承载力的影响。最后进行仿真与实验的对比。结果表明,故障前后转子最大位移幅值误差小于3.9%,验证了所建模型用于计算系统动态承载力的有效性。

The dynamic capacity of the active magnetic bearing(AMB)system changes due to its channel failure.The accurate calculation of dynamic capacity is required to determine AMB system operation conditions.However,the AMB system model with partial channel failure in existing studies greatly deviates from reality.In order to improve the model accuracy for calculating the dynamic capacity of the AMB system,considering the external load and initial unbalance mass from the rotor,this paper establishes the four degrees of freedom(DOF)AMB system models with or without channel failure.Based on the system model,dynamic capacity can be calculated with the relations between external load,rotor displacements,and channel current.Firstly,based on the single DOF AMB system model,this paper elaborates on two critical states related to rotor mass:rotor displacement critical state and channel current critical state.Then,the 4-DOF model is established considering external load and initial unbalance mass from the rotor.Secondly,the initial unbalance mass from the rotor is calculated according to the rotor displacement amplitude,which changes by placing various external loads on the rotor.Finally,according to the two critical states,the dynamic capacity of the system with or without partial channel failure is calculated,and the influence of control parameters is analyzed for the AMB system with partial channel failure.By changing the external load value or rotor mass on a single DOF AMB system,we find that the rotor displacement amplitude reaches the critical value(collision value)for the low-mass rotor,and the channel current reaches the critical value(saturation value)for the big-mass rotor.The ratio of rotor displacement amplitude at the stretch side and non-stretch side is related to the load axial position.Therefore,the axial position sign of the load can be determined according to the ratio value.The rotor displacement amplitude can be obtained by substituting the dynamic load into the model,and the error of dynamic load of calculated and set value is less than 1.5%.The dynamic load calculated by rotor displacement amplitude at 4-DOF from experiment data can also be mutually verified,proving the method of calculating dynamic load from rotor displacement amplitude works.Experiments at different rotor speeds and additional extern loads are conducted.The result shows that the maximum amplitude error in rotor displacement from the experiment and simulation does not exceed 3.9%.By changing the proportional and differential coefficient value in a limited range of the AMB system with lower channel failure,the maximum displacement amplitude error of the simulation and experiments does not exceed 3.5%.Since the rotor mass of the experiment platform is relatively small,the dynamic capacity of the AMB system with or without failure can be calculated from the rotor displacement amplitude.The dynamic capacity of the AMB system with/without failure is 3600 N/5100 N.The following conclusions can be drawn through simulation analysis and experiments:(1)As the dynamic load changes,the AMB system has two critical states.That is,rotor displacement amplitude and channel current reach a critical value.According to the critical states,the dynamic capacity of the AMB system can be calculated.The value of the dynamic capacity increases first and then decreases in the process of rotor mass increases.(2)The error of the maximum displacement amplitude of simulation and experiments does not exceed 3.9%without channel failure,and the error does not exceed 3.9%with channel failure.It indicates that the model can be used to calculate the dynamic capacity of AMB systems with or without channel failure.(3)The dynamic capacity of the AMB system is associated with the proportional and differential coefficient values,but the adjustment range is limited.