High-Precision Field Dynamic Balancing for High-Speed AMB-Rotor Considering Unbalanced Magnetic Pull

Active magnetic bearings (AMBs) are developed aiming at higher speed and lower vibration, which imposes improvement of rotor dynamic balancing. Field dynamic balancing based on system synchronous response for rotor unbalance is widely used for AMB-rotors, but its precision can be affected by unbalanced magnetic pull (UMP) since it accounts for an obvious part of the AMB synchronous force during balancing process. Consequently, a high-precision field dynamic balancing method considering UMP is proposed to mitigate the adverse effect of UMP. First, the dynamic model of AMB-rotor system considering UMP is established, then the difference between the system response of rotor unbalance and UMP is analyzed in the autocentering control mode. Second, based on the difference analysis, a UMP separation method is used at two rotational speeds to calculate UMP and extract corresponding AMB compensation current component. Hence, the accurate correction masses can be calculated according to the equivalent relationship between the residual unbalance and corresponding AMB current. Finally, experiments are carried out on a turbomolecular pump prototype to verify the effectiveness of the method. The experimental results demonstrate that the proposed method achieves higher precision and lower vibration at operating speed.