Integrated Radial-axial Magnetic Bearing with Variable Permanent-Magnet Bias Flux In Situ

Bias magnetic flux plays a crucial role in the performance of active magnetic bearings. However, the bias flux produced by NdFeB or SmCo materials in traditional permanent-magnet (PM) bias bearings cannot be adjusted, resulting in inflexible bearing performance. To improve the controllability of the PM bias flux in the integrated radial-axial magnetic bearing (RAMB), this article proposes a new design that uses a low coercivity AlNiCo magnet and equips a magnetization coil. By controlling the current of the magnetization coil, the magnetization state and bias flux of the AlNiCo magnet can be adjusted in situ, thereby improving the force characteristics and rotor iron losses of the PM-biased RAMB. The designed RAMB is analyzed and verified by the 3D finite element method and the analytical model based on Preisach’s hysteresis theory and magnetic circuit method. The proposed design offers a new idea for magnetic bearing structure and control.