Superconductor bearings, flywheels and transportation

Abstract

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN 2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors

“…1,2 As a result, these materials are attracting increasing interest for many applications in which they can act effectively as strong quasi-permanent magnets, including rotating machines 3 and stable magnetic levitation devices. 4 Bulk superconducting magnets consist typically of cylinders of 10-50 mm in diameter and 10-20 mm in height. 5 Associated measurement and characterization methods by both destructive and non-destructive techniques have developed naturally as the ability to melt process these materials has evolved.…”

Lumped-Parameter Model to Describe Dynamic Translational Interaction for High-Temperature Superconducting Bearings

“…These slight changes in material properties produce much closer agreement in translational force estimates, although the vertical force is slightly over predicted further away from the center. The critical current densities for YBCO material can range from 10-100 kA/cm 2 [2]. As compared to the FEM analysis, the lumped parameter model shows a significant falling off of force near the edges of the bulk HTSC, which is not observed in the test data.…”

“…ESEARCHERS are pursuing high temperature superconducting bearings for applications such as flywheel energy storage where low losses are critical for retaining stored energy [1], [2], [3]. Typically, these bearing systems consist of an array of permanent magnets that are stably-levitated over an array of bulk high temperature superconductors (HTSC) such as yttrium barium copper oxide (YBCO).…”

The Effect of Sm Addition on the Microstructure and Superconducting Properties of YBCO Bulk Superconductors

“…Various practical applications of Y-Ba-Cu-O (YBCO) bulk superconductors are mainly based on their ability to trap large magnetic fields [1,2]. It has already been shown that these materials can trap magnetic field by order of magnitude higher than the best ferromagnets [3].…”