Comparison of the dynamic response of radial and tangential magnetic flux thrust bearings

Abstract

Theoretical predictions were made for the dynamic performance of a tangential flux magnetic thrust bearing. A prototype bearing was built with the stators and rotors made from tape wound strip. The performance of this bearing was measured and compared to the theoretical predictions and also to the performance of a radial flux thrust bearing. Tangential flux bearings are intrinsically amenable to construction from tape wound cores. Tape wound cores come in high saturation alloys like supermenduer which can give the bearing a high force to size ratio. The thin tape laminates give the bearing a broad frequency bandwidth. By comparison it is shown that it is difficult to make a laminated rotor magnetically efficient for radial flux bearings. A test rig is described that was built to measure the performance of the tangential flux bearing. A power amplifier with current feedback provided dc and harmonic current to the coils. A load cell was built into the test rig to measure the axial thrust, an inductive/hall sensor was included to measure the coil current, and a hall probe to measure the gap flux. Index Terms-Magnetic bearing, magnetic circuit, tape wound core. NOMENCLATURE Half pole face area. Laminate thickness or thinnest dimension of flux path. Denominator terms. Stacking factor. Magnetic force per stator. Magnetic flux. Coil current. Path length. Coil inductance. Inductive parts of laminate reluctance. Number of poles per stator. Numerator terms. Turns per coil times bias current. Turns per coil times control current. Permeability of metal. Permeability of air. Relative permeability of metal Permeability normal to laminations. Permeability tangential to laminations. Density of laminate metal.

Dynamic performances of a magnetic thrust bearing based on new soft magnetic composites

“…But for magnetic thrust bearings (MTBs), because of the magnetic path including both radial and axial parts, both stator and rotor are very difficult to be split into laminated structure to eliminate eddy currents. Some scholars have tried to use foil winding 5 or stator blocks 6 methods to make bearings, but the results show that the two methods cannot effectively reduce eddy currents. In fact, MTBs are basically made of solid steel in the industrial application.…”

Dynamic Stiffnesses of Active Magnetic Thrust Bearing Including Eddy-Current Effects

“…Although different configurations of the thrust bearing have been studied in the past few years [1], [2], the configuration constructed of solid stator and rotor made of conventional solid ferromagnetic material with radial flux path orientations is still the most commonly used in practice for its simplicity and cost effectiveness.…”