Development of 50-kW-Class High-Temperature Superconducting Induction/Synchronous Motor With Continuous Drive Characteristics from Room Temperature

We investigate the rotational characteristics of a 50-kW-class high-temperature superconducting induction/synchro- nous motor in superconducting and non-superconducting states. The prototype motor was first placed in liquid nitrogen, and the efficiency contour was obtained. The liquid nitrogen was then gradually removed from the motor under the partial load (10 kW) condition. This showed that continuous operation is possible even at temperatures exceeding 130 K. Furthermore, we succeeded in driving at 11% of the rated output, even at room temperature. As a result, a practical high-temperature superconducting motor that can continue to operate with reduced output even when the cooling system fails could be realized.

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.