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

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 self-protecting. 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.