Field Dynamic Balancing for Magnetically Suspended Turbomolecular Pump

Abstract

A field dynamic balancer is crucial to the applications of magnetically suspended turbomolecular pumps. Therefore, this paper presents a novel field dynamic balancing method based on autocentering control mode without any additional instrumentation. Firstly, the dynamics of the active magnetic bearing rotor system with unbalance are modeled. Through model analysis, it was found that making the rotor rotate around the geometric axis can improve the accuracy of dynamic balancing. Secondly, the relationship between the correcting masses and the synchronous currents based on the influence coefficient method is established. Then, an autocentering controller is designed to make the rotor rotate around the geometric axis. The synchronous currents can be detected and extracted by the current transducers to calculate the unbalance correction mass. Finally, the experimental results show that this novel field dynamic balancing method can effectively eliminate the majority of rotor unbalance. Compared with the original unbalance of a rotor, the synchronous current in the A-end has been reduced by 71.4% and the synchronous current in the B-end, by 90.8% with the proposed method.

Calculation of Stationary Magnetic Fields Based on the Improved Quadrature Formulas for a Simple Layer Potential

“…A robust closed-loop control strategy for systems with active magnetic bearings requires calculations of the mentioned parameters over the entirety of the operating range [4]. Precision calculations of magnetic fields are required to successfully implement complicated magnetic phenomena, like magnetic levitation [5,6]. A more detailed expression of the magnetic force is an important optimization approach to controlling open-loop unstable magnetic systems [5].…”