Fourier-Based Modeling of a Slotless Hybrid Homopolar Radial Magnetic Bearing with Passive Axial Stabilization

Among active magnetic bearings (AMB), homopolar hybrid AMB (HH-AMB) generate a homopolar bias magnetic field using permanent magnets (PM) to reduce Joule and iron losses. The iron losses are further reduced by the slotless topology of the HH-AMB (SHH-AMB). Analytical models of the topology have been implemented using magnetic equivalent circuit (MEC) and Fourier-based (FB) methods. This paper proposes a FB model of a variant of the SHH-AMB topology that has additional saliencies on the rotor to provide an axial stabilization. The validity of the results is assessed with a finite element analysis (FEA) and experimentally, with measurements performed on a prototype of the bearing under study.

I. Introduction

Active magnetic bearings (AMB) allow a contactless stabilization of a rotating body through electromagnetic forces. Among the various types of AMB, homopolar hybrid AMB (HH-AMB) generates a homopolar bias magnetic field with permanent magnets (PM) [1]. This topology eliminates Joule losses associated with bias current, thanks to the action of PM. The homopolar nature of the bias magnetic field reduces the iron losses associated with fluctuations in the magnetic field as the rotor spins. These latter losses can be further reduced by placing the armature winding in the airgap, thus avoiding the field discontinuity produced by slot openings.