Abstract-This paper studies the technical viability of a frictionless rotating bearing model comprising one inner rotor part with discontinuous rings with permanent magnets and one outer stator part with discontinuous rings with high temperature superconducting bulks, distributed on a geometric arrangement that guarantees enhanced levitating and guidance forces using the zero field cooling technique. Extensive Finite Element model simulations were carried out to estimate levitation and guidance forces depending on the air gap dimensions. Eccentricity and axial displacement of the rotor are estimated depending on the external radial and axial forces applied to the rotor. Finally, the proposed design of a viable and feasible frictionless bearing prototype is foreseen.
Abstract-This paper presents the conception, simulation and experimental evaluation of magnetic bearings based on NdFeB magnets and zero-field-cooled (ZFC) YBCO bulk superconductors to replace the bearings of a standard electric machine. Advanced research on HTS magnetic levitation has been carried out for the construction of large scale flywheels or for industry applications. However, those approaches used fieldcooled (FC) superconductors, whereas the approach shown in this paper uses ZFC superconductors. Actually, as previously shown by the authors, ZFC implementation presents much less AC losses. The approach in our horizontal flywheel research follows the ZFC-maglev structure, where the linear track was closed into a circular one with the same diameter of the superconductor magnetic bearing. The conception and geometric placement of magnets and superconductors was designed to keep symmetry along the rotating axis and minimizing air gaps. A 3D finite element model was built for simulation and validation of the effectiveness of the solution. Experimental validation was then achieved measuring the balanced and unbalanced rotor lifting and guiding forces.
Based on the levitating design of the Zero-Field-Cooled (ZFC) Maglev previously developed, a novel horizontal ZFC superconductor magnetic bearing (SMB) is currently being developed. However, simulations have shown that its stator and rotor made of YBCO bulks and NdFeB permanent magnets (PM), respectively, present significant magnetic discontinuities. These produce asymmetries on the bearing rotation and several stable and unstable position angles that prevent the SMB from rotating smoothly, leading to a step motor like sort of rotation. Those drawbacks are now avoided by using ring shape PMs, leading not only to a smooth rotation of the SMB but also increasing its stability. New three-dimensional finite element method simulations and a set of experimental tests with the new SMB show in this paper the viability and increased performance when ring shape PMs are used. Finally, experimental results using the prototype also show that the model fits very well with the laboratory test results.
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