Combined Active Magnetic Bearing Topology to Control 3 Degrees of Freedom

This paper proposes a compact topology for an active magnetic bearing (AMB) that integrates both radial and axial control into a single structure. A key innovation of the design is the use of a single bias magnet whose flux is shared between the axial and radial directions. At the same time, the active control flux paths remain separated, which is essential for implementing a simple and decoupled control concept. Moreover, the active flux does not pass through the bias magnet, allowing for strong active magnetic fields. To evaluate the effectiveness of the proposed design, finite element simulations were performed using ANSYS Electronics. The combined bearing exhibits significantly less negative stiffness compared to separate radial and axial bearings, along with increased force-to-magnetomotive force ratios. To quantify this improvement, the magnetic stiffness compensation coefficient is introduced, relating these parameters to each other. In addition to its magnetic performance, the design offers practical advantages: since the rotor is not mechanically interlocked with the bearing, it can be installed or removed without disassembling the bearing system. This makes the proposed solution especially attractive for high-speed and maintenance-sensitive applications.