I. Introduction
Recently, much research has secured the core technology for eco-friendly and high-efficiency electric propulsion systems to cope with global environmental regulations in the transportation field [1], [2], [3], [4]. To respond to a market-led strategy to lead the global electric propulsion aviation market with high-temperature superconductor (HTS) technology, research to get the core technology specialized in HTS racetrack coils, including the cryogenic cooling system with liquid hydrogen, has been initiated around the world [5], [6], [7], [8], [9], [10], [11], [12].