Current Status of and Challenges for No-Insulation HTS Winding Technique

Abstract

In this paper we summarize what we have learned so far and discuss key technical challenges that face the HTS “NI” magnet wound with the no-insulation (NI) technique, focusing one of its beneficial features, self-protecting. We first describe the basic features of the NI winding technique, including lumped circuit and distributed network models. Next, we present results of a stand-alone NI magnet composed of REBCO double-pancake coils, showing that the magnet is indeed selfprotecting. In the last part of this paper, we discuss the technical issues, often called “NI behaviors”, objectionable demerits that still remain, particularly in nested-coil NI magnets. These include charging delay, non-linear magnet constant in time-varying operation, unbalanced forces that can overstrain the conductor. We conclude the paper with our conviction, and optimism, that the NI winding technique is viable for HTS magnets, high-field and large electric power devices.