Loading capacity, rotation loss and torsional oscillation research on an Evershed-type hybrid superconducting bearing used for micro-thrust measurements

Abstract

Characterized by very low rotational drag, applications of high temperature superconductor (HTS) bearings have been expanded in some high precision instruments. We developed a sensitive magnetic suspension stand based on an Evershed-type hybrid HTS bearing to measure the micro newton level thrust. The hybrid HTS bearing is to use the strong attractive force of a permanent magnet (PM) biased bearing to support main loading in the bearing, while the instability in the PM biased bearing was compensated by the magnetic stability from an HTS bearing. Compared to the single PM/HTS bearing, the hybrid HTS bearing is intended not only to support larger load and but also to suppress the rotation loss and levitation drift. Loading capacity, loss and damping torque were explored at different design parameters such as bearing gaps L1, L2, field cooling height (FCH) of bulk HTSs. Spin down testing suggested that the loss of the hybrid HTS bearing can be reduced by raising the HTS bearing gap L2 or reducing the field cooling height. The hybrid HTS bearing showed a typical oscillation behavior in the extreme low frequency, and torsional pendulum testing suggested that the spring constant k of the hybrid HTS bearing can be as low as 36.39 μN·m/°. A micro-thrust stand based on the hybrid HTS bearing was established to test an electrospray thruster in the vacuum chamber, and the measurement result of 26.61 μN presents the ability of micro-thrust stand to achieve μN level testing.

Analysis of critical current inhomogeneity in r–z plane of GdBCO superconducting bulk and simulation of flux jumps during pulsed field magnetization

“…The large-grain RE-Ba-Cu-O (RE is an abbreviation of Gd and rare earth elements) high-temperature superconductor (HTS) has great potential to trap up to 17.6 T magnetic fields (B T ) [1][2][3]. For a number of promising applications, such as superconducting bearings [4], flywheel energy storage systems [5], aviation electric propulsion devices [6] and nuclear magnetic resonance(NMR) [7], the ability of HTS bulk to obtain high magnetic fields could be crucial and revolutionary.…”