Modelling and Validation of Rotor-Active Magnetic Bearing System Considering Interface Contact

Rotor-active magnetic bearing (rotor-AMB) system is increasingly applied in rotating machinery such as blowers, compressors, vacuum pumps, etc. However, due to the coupling of interface contact (such as bolt-joint surface and cylindrical-joint surface) formed by impeller assembly and AMB supporting, the rotor will vibrate at a modal frequency once levitated, which causes system instability and equipment breakdown. Therefore, it is essential to reveal the principle of this vibration. In rotor modelling, interface contact is equivalent to an additional stiffness matrix based on a massless spring unit. The value of the matrix is obtained by energy law. Subsequently, interface contact’s influence is considered an internal disturbance in the rotor-AMB system. This modelling method is validated by different test rigs. Through rotor response and stability analysis of different test rigs, it is found that rotor modal resonance mode depends on contact interface parameters (such as bolt pre-tightening force). Based on these results, stability analysis is carried out to study the general relationship between system stability and contact interface parameters, which will further reveal the vibration mechanism and guide the following maglev machine structural design to avoid this vibration.