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.
The outgas from constituent materials in the vacuum jacket of a cryogenic vessel may seriously affect the degree of vacuum and it leads to deterioration of heat insulation performance. We measured the outgassing rates from each material that comprises the vacuum vessel. We also measured the effect on outgassing rate when the materials are heated to remove the gas from the materials before measurement. Based on experimental results, the effect of heat treatment for each material based on the outgassing model was discussed. It was found that coating the materials with GFRP is effective for reducing the outgassing rate.
This paper presents the estimation of machine parameters for a superconducting power transformer. The estimation technique was developed using simplified φ- L magnetizing characteristics, the Ralston's Runge-Kutta method on spreadsheet software and a genetic algorithm. Using this estimation technique only for inrush current waveform, machine parameters and switching conditions of the superconducting transformer were estimated. EMTP-ATP simulation of the inrush current was carried out using these machine parameters. Consequently, the EMTP-ATP simulated waveforms reproduced the waveforms measured.