Progress on electrodynamic passive magnetic bearings for rotor levitation

Abstract

Electrodynamic suspension exploits repulsive forces due to eddy currents to produce positive stiffness by passive means, without violating the Earnshaw stability criterion. Systems employing this principle to levitate a rotor radial and/or axial degrees of freedom are called electrodynamic bearings (EDBs). Since the eddy currents can be induced either by using alternating current supplied electromagnets or by the relative motion between a conductor and a constant magnetic field, the research on EDBs has developed many different configurations. The present paper reviews the literature on electrodynamic passive magnetic bearings to analyze the evolution of this technology toward completely passive, stable, rotor levitation, and to compare the EDBs performance with other common magnetic bearing technologies. Radial and axial EDB technologies are reviewed attempting to create an organized connection between the works and to discuss some critical issues that still preclude the use of EDBs in industrial applications.