Linear State-Space Representation of Heteropolar Electrodynamic Bearings With Radial Magnetic Field

Abstract

Electrodynamic bearings can operate without active control means. In that case, the dynamic behavior of the bearing relies solely on passive electromagnetic phenomena which can be studied using specific models. In recent years, linear state-space representations linking the forces and the relative motion between the stationary and moving parts of such a bearing were obtained without making any assumption on the kinematics of the rotor axis. However, significant limitations remain regarding the topology of the bearing. As regards heteropolar bearings with radial magnetic field, the latter refers to: 1) the number of winding phases; 2) the number of pole pairs of the permanent magnets (PMs) and winding; 3) the presence of PMs at the rotor or at the stator; and 4) the presence of a ferromagnetic yoke attached to the winding. This paper presents a model free of these limitations. Compared with existing models, few additional complexities are introduced in the state-space representation. As a result, the dynamics of a wider range of heteropolar electrodynamic bearings can now be studied with a linear model.