Basic Characteristics of Improved Bearingless Motor with Passive Magnetic Bearings

In this paper, basic characteristics of a bearingless motor with passive magnetic bearings (PMBs) are presented. A bearingless motor is actively controlled in two perpendicular radial movements, and is passively stable in the other three degrees of freedom, i.e., axial and conical movements. With PMBs, the stiffness is enhanced in axial and conical movements. To enhance stiffness, an improved machine has been designed. The experimental results of basic characteristics in the proposed machine are presented. The experimental results are compared to the calculated ones using three-dimensional finite element method (3D-FEM). The experimental results of the proposed machine with and without PMBs are compared. It is presented that a bearingless motor with PMBs has significantly enhanced the axial and conical stiffness.