Dynamic Analysis of Active Magnetic Bearing Rotor System Considering Alford Force

This paper studies the influence of Alford force on permanent magnet turbo-expander/generator supported by active magnetic bearings. The differential equations of rotor motion are established, magnetic bearing force that controlled by the PID and Alford force are considered into the equations. Based on the simulation and experiments, the response of the rotor is solved. The results show that after the introduction of Alford force, the amplitude of the rotor increases and the axis trajectory of the impeller side gets larger. The influence of Alford force can be mitigated by adjusting the control parameters which improves the support characteristics. Both the simulation and experiments show that for the PID controller, the differential coefficient has an obvious effect on mitigating the influence while the effect of the proportional coefficient is relatively small. Therefore, as a rotor supported by active magnetic bearings is different from traditional bearings, it is necessary to consider the effect of the control parameters and the differential coefficient needs paying more attention to.