Continuous Critical Current Measurement System Of High Temperature Superconductor Tapes Based On Magnetic-circuit Method

High temperature superconductor (HTS) materials have great application potentialin electric power, energy, and environmental protection fields; at present, HTS wires(tapes) have gradually realized industrial production. However, HTS tapes belong toceramic materials and the mechanical property of HTS tapes is extremely weak. Duringproduction and application, HTS tapes tend to generate local defects, where the criticalcurrents are reduced. When HTS tapes are used in electric application, local defects willbecome hot spots and limit the performance of the entire device, which is one of themost important reasons to restrict wide application of HTS tapes. As a result, beforeHTS tapes are used for electric apparatuses, to continuously measure the critical currentof HTS tapes is necessary.This thesis researches on a novel method to continuously measure thecritical current of HTS tapes. This method uses two magnetic circuits to exciteand measure the remnant magnetic moment of HTS tapes and calculates thecritical current accordingly, so it is named Magnetic-Circuit (MC) method. Thisthesis gives the derivation of the principle equation and discusses this method’sadvantages accordingly. And the principle is verified by numerical simulationusing finite element method. The method has two outstanding advantagescompared to other available methods worldwide:1. In principle this method avoids measurement noise aroused bymechanical vibration; as a result, it can realize measurement with highrepeatability, stability and speed and the cost in mechanical engineeringis sharply saved.2. It can measure HTS tapes with magnetic substrates (RABiTS).The first advantage of the apparatus has been verified by our group’sprevious work. This thesis introduces the construction process of the apparatusbased on the Magnetic-Circuit method and gives the specifications of theapparatus. And the second advantage of the Magnetic-Circuit method isdemonstrated by experiments. Moreover, the practical application of theapparatus is verified by measurement of industrial length of HTS tapes. In the end, this essay points out the methods for assessing HTS tapes’ performances,including statistical analysis, Fourier analysis and so on. And the assessmentresults of representative tapes from main HTS manufacturers worldwide areprovided.