I. Introduction
The Electric drive of transportation equipment, such as automobiles, ships, and aircraft, is considered to be an essential technology for a low-carbon society in the future [1]. In such transportation equipment, the drive motor is installed in a limited space within the moving body; thus, it is necessary to increase the mechanical output (and/or torque) per unit volume (and/or weight) as much as possible. As a candidate that satisfies these conditions, a motor using a high-temperature superconducting (HTS) conductor capable of transporting a large current with low loss has attracted considerable attention. Therefore, vigorous research and development has been carried out in ships [2], [3], [4], [5], [6], land transportation equipment [7], [8], [9], and aircraft [10], [11], [12], [13], [14], [15]. Ship propulsion motors have been successfully prototyped as full-scale motors from several hundred kilowatt to megawatt classes, and rotation tests have also been conducted.