Parameterized Electromechanical Model for Magnetic Bearings with Induced Currents

Abstract

The purpose of this paper is to present a parameterized electromechanical model taking into account both the electromagnetic nature of the forces acting inside a magnetic bearing and the general rotating machinery aspects, as well as their interactions. This model specifically includes the effect of induced currents. These induced currents in the bearings are submitted to inductive and resistive effects, as well as skin effect, and the influence of these effects is considered. It is shown that the stability of a bearing may be analyzed, based on this model. The parameters of the model are identified from experimental results for an existing semi-passive magnetic bearing, and it is shown that the forces predicted by the model are close to experimental measurements.

Null-Flux Radial Electrodynamic Bearing

“…Equation (24) shows that the induced current is such that this average force is non-zero, and that the maximum average force is obtained when the phase change between the EMF and the current isφ m = π/2, i.e., when the winding is purely inductive. This positive influence of an inductive behavior has also been shown in [7], [12], and [21]. Of course, having a high induced current amplitudeÎ m has a positive effect on the stiffness.…”

“…They are zero when the winding has a purely inductive behavior. SinceF φ has a bad effect on the stability of the bearing [7], [12], this highlights the importance of the inductive behavior of the winding.…”

“…Another model where the dynamics are represented by mechanical components determined on the basis of a power balance approach is proposed in [6]. The latter model has already been used to study stability issues [7]. In addition, the differences between the stability issues of homopolar and heteropolar electrodynamic bearings were studied in [8], on the basis of an unified model derived from the analytical solution of the magnetic field.…”

Unified modelling of passive homopolar and heteropolar electrodynamic bearings

“…The literature on electrodynamic suspension of rotors provides numerous examples of experimental measurements on radial electrodynamic bearing systems. Most of the experiments are performed for an off-centre shaft at constant spin speed (quasistatic condition) [4,17,18,20], but this kind of analysis does not represent completely the suspensions' dynamics. The study of a system that successfully realizes the radial suspension of a rotor using electrodynamic bearings has been presented by Filatov and Maslen [9].…”

“…A modelling procedure similar to that proposed by Filatov and Maslen, based on the electrical time constant, was presented by Kluyskens et al [16,17]. In these works, the influences of rotating and nonrotating damping on the whirl stability are presented.…”