Nonlinear Modeling and Analysis of Electromagnetic Bearings With Permanent Magnets for Bias

Abstract

This article describes high fidelity modeling of electromagnetic (EM) bearings with permanent magnets (PM) used to supply bias current. We analyze both the PM and EM parts of the system. Magnetic circuit theory is first used to gain insight into the magnetic forces and allows for the dynamic analysis of a rigid rotor coupled with the magnetic bearings. The results reveal that the magnetic forces are a strong nonlinear function of the rotor offsets from its equilibrium position. Next, the validity of the simplifying assumptions is examined with the aid of the finite element method. Comparisons of the magnetic forces are presented and discussed.