Effect of Temperature on Rotation Loss in a Superconducting Device for Microthrust Measurement of Electric Propulsion System

Abstract

Accurate measurement for long-term accumulating momentum of electrical propulsion (EP) requires the microthrust stand with high performance. A microthrust-measuring device using high-temperature superconductor magnetic levitation (HTSML) is designed to remove connecting interferences for better evaluation of EP thrusters. Levitating rotation loss is the main factor that affects measuring accuracy of the HTSML device. In this paper, we propose a new method to measure the accumulating momentum. A vacuum experimental setup that can control the temperature of YBCO bulk was built up to investigate the rotation loss at low speed. Effects of temperature and field cooling (FC) height on the coefficient of friction μ are analyzed. By analyzing the basic phenomenon of the rotation friction in the low speed range less than 30 Hz, the low speed rotation can be divided into three different phases. When the rotation frequency is closed to the natural frequency of the HTSML device, oscillation happens and leads to serious rotation loss. The friction loss after the oscillation is very steady and can be used in the measurement of accumulating momentum. The large FC height and temperature can diminish the rotation loss, and increasing FC height could diminish rotation loss dependence of temperature. Although the experimental measurements show good repeatability, large rotation loss (10 -4 ∼10 -3 ) in the experimental setup means that this setup should be further improved.

Dependency of hysteretic loss on speed and tilt in a rotating superconducting magnetic bearing

“…Friction free superconducting bearings are suitable for high-speed applications, which include linear as well as rotational setups, as shown by many groups in recent years [1][2][3][4][5]. Although there is no mechanical friction in the bearing, other dissipating losses might be generated [6][7][8][9]. For rotating applications these losses are highly depended on the rotational speed [10][11][12], on the spatial displacements [13] and the magnet quality [14].…”

“…To verify this assumption, we designed a new calorimetric measurement setup that allows to reproduce the rotation of a tilted magnet in a laboratory environment. Different from the usual approach of free spin down test for loss evaluation [7,21,22], we can introduce a defined tilt after a parallel fieldcooling of the magnet at a fixed cooling height. The general measurement design is similar to a setup described by other groups [23,24].…”