Matching Design of Active Magnetic Bearing and Elastic Support Vibration Isolator

In modern industries, high-speed machinery occupies a fundamental place. However, rotating machinery will inevitably produce a variety of structural noise and vibration, so much as vibration isolation of rotating machinery has become the technical bottleneck of acoustic radiation level control in some fields. Generally, vibration isolation means can be divided into active vibration isolation and passive vibration isolation, among which the most representative are active magnetic bearings (AMBs) and vibration isolators, respectively. The combination of active magnetic bearings and vibration isolators is widely used in rotating machinery because of its excellent effect in vibration and noise reduction. In practice, the type of vibration isolators are often directly selected according to the weight of the machine, and the stiffness of active magnetic bearings is often determined by the manually adjusting control parameters through trial and error.

This paper concentrates on the analysis of the vibration transmission mechanism of the active magnetic bearings coupled with the passive foundation elastic support (vibration isolators). A 30 kW prototype pump is taken as an example to help describe the research method. The model of the pump is first established. The stationary pump components (the pump case) and the rotor are respectively modeled through the finite element method and converted to substructure modal expression after low-order modal extraction. The bearing force is simplified to spring-dampers with equivalent stiffness and equivalent damping relating to the exciting frequency. The foundation elastic supports (vibration isolators) are simplified as three-dimensional spring-dampers. After the modal transformation, the matching relation of the system can be expressed as the design problem of the minimum vibration of the machine foot. Based on the model, this paper then investigates the matching relation of the AMBs and the vibration isolators and proposes a dynamic vibration isolation design method for the rotor-AMBs-flexible support system. On the basis of the frequency-domain response of the original design, this design method is applied to the prototype pump. The results show that the design method based on matching relation has good performance in vibration isolation.