Conduction-Cooled YBCO HTS Current Lead for SMES Application

A 500 A class high temperature superconductor (HTS) current lead has been designed, fabricated and tested for a superconducting magnetic energy storage system (SMES) cooled by conduction cooling. The current lead is made of YBCO tapes and cooled directly by a two-stage cryocooler. Its warm end is cooled by the first stage and the cold end is cooled by the second stage of the cryocooler. The SMES generates a magnetic field of 7 T at the operating current and as the current lead is possibly exposed to its flux-flow range, the critical current of the YBCO current lead is measured as a function of magnetic field and the impact of magnetic field on the critical current is calculated and analysed. Based on that, two lead schemes are presented and analysed technically and economically. The experimental results show that the YBCO current lead has better thermal conduction capacity and current-carrying capacity than the Bi2223 lead does.