Method with reliable accuracy and fast speed for measuring operational current of HTS NI closed-loop coils in steady persistent-current-mode  

作　　者：Li Lu Wei Wu Xin Yu Zhuoyan Zhong Kai Li Chengyun Pan Mengzhu Li Zhijian Jin 

机构地区：[1]School of Electrical Engineering and Electronic Information,Shanghai Jiao Tong University,Minghang District,200240 Shanghai,PR China [2]Shanghai Superconductor Technology Co.,Ltd.,Pudong New District,201203 Shanghai,PR China [3]CRRC Changchun Railway Vehicles Co.,Ltd.,Changchun 130062,Jilin,PR China

出　　处：《Superconductivity》2024年第1期65-73,共9页超导（英文）

基　　金：supported by National Natural Science Foundation of China(NSFC)under project 51977130.

摘　　要：This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed‐loop coils are promising for many easily‐quenching direct‐current(DC)applications,where their performance is determined by magnetomotive forces,total number of turns,and dimensions.As the primary interface parameter in an application system,the operational current must be accurately and rapidly measured.Generally,this is achieved by dividing the measured magnetic field by the coil constant.However,even if the influence of the screening current induced field(SCIF)is not considered,existing methods for the coil constant may be disturbed by the performance and location of Hall sensors,or experience a long measuring period.Therefore,a relatively accurate and fast method is proposed in this study,which is based on adjusting the output current of the adjustable power supply and monitoring the coil voltage as an indicator.The proposed method was validated through experiments and simulations using an equivalent circuit model coupled with a finite element method(FEM)model,and its current accuracy can be equivalent to the resolution of the employed power supply.It was demonstrated that this method reduced the requirements for Hall sensor’s performance and location,and has a more reliable accuracy in contrast to the simulation method.Compared to the experimentally conventional method,the proposed method presents a significantly faster speed.The impact of the SCIF was considered and proven to be negligible for the tested pancake coils.Even for coils whose coil constant vibrates owing to the SCIF,this method can be adapted to directly measure various operational currents.Furthermore,it was demonstrated that the measurement error can be influenced by the current discrepancy among turns when the coil is not in the steady PCM,and a procedure for reducing this error was proposed.

关 键 词：Operational current HTS NI closed‐loop coils Measurement method Adjustable power supply Coil voltage 

分 类 号：TM26[一般工业技术—材料科学与工程]