Yokeless radial electrodynamic bearing

Abstract

Due to the presence of a ferromagnetic yoke in passive electrodynamic magnetic bearings, the stiffness associated with their radial centering force becomes negative under a critical speed. This leads to instability problems and to the necessity of using mechanical launch bearings at low speed. In this paper, an electrodynamic bearing without ferromagnetic yoke is proposed. An analytical 2D model of the bearing is presented and used to perform a first analysis of the bearing. The force predictions correspond to expectations: the stiffness never reaches negative values. It is also shown that for given geometrical dimensions, the performance of the studied bearing can be significantly improved by choosing the appropriate number of phases and number of pole pairs of the winding