Research on analytical bearing capacity model of active magnetic bearings based on magnetic saturation

Researches on active magnetic bearings (AMBs) are mainly based on equivalent magnetic circuit (EMC) method with the assumption that there is no magnetic saturation in magnetic circuit. However, this assumption about magnetic saturation is no longer valid for special solutions, such as aero-engines. In this case, limitations exist for the application of EMC method. This research focuses on an analytical bearing capacity model for AMBs based on a non-linear magnetic circuit method (NMCM) with magnetic saturation taken into account. First, the error factors of EMC method are analysed by using finite element analysis software when the air gap increased. Then, aiming at the main factors, including fringing flux, flux leakage and magnetic saturation, the air-gap magnetic flux model and the flux leakage model are developed based on the magnetic field division method. On this basis, a NMCM based on magnetic saturation is proposed to create the analytical bearing capacity model of AMBs. Additionally, the analytical model is verified by comparing with the results of finite element analysis and experiments. Eventually, the analytical model of hybrid magnetic bearing with single degree of freedom based on NMCM is verified by experiments.