Null-Flux Coils in Permanent Magnets Bearings

In this paper, the stability analysis of a new permanent magnets (PMs) bearings is presented and discussed. The suspension is assured by the repulsive force of properly shaped PMs placed on both the stator and the rotor. Then, exploiting currents induced on a system of null-flux coils attached to the stator, a stabilizing force for the translation of the center of mass of the rotor is obtained. The performance of the proposed bearing is investigated by a research code, previously developed at DESTEC and capable to simulate six degrees of freedom electromechanical devices.

I. Introduction

The nowadays availability of rare-earth permanent magnets (PMs), (e.g., NdFeB) characterized by high values of remnant field, has made possible to conceive a new class of systems where the suspension is assured by the repulsion of properly shaped PMs [1]–[4]. An application example is flywheel energy storage systems, which are considered to be an attractive alternative to conventional electrochemical batteries [5], [6]. As known, stability of levitation for systems based on PMs only, is prevented by Earnshaw’s theorem and Braunbeck’s extension [7].