Development of Stirling Cryocooler for Electric Bus Superconducting Motor

Abstract

Synopsis:Recently, practical applications of high-temperature superconducting (HTS) wires are being promoted.Superconducting motor is one of the application for HTS wires, with the advantage of expected higher efficiency. As the performance of the wire was improved, the development of a superconducting motor has been actively conducted. To demonstrate the higher efficiency of electric vehicles driven by a superconducting motor, the development of a superconducting motor and its cooling system has been performed through the joint research of Sumitomo Heavy Industries, Ltd. (SHI) and Sumitomo Electric Industries, Ltd. (SEI). To improve the total efficiency of a superconducting motor system, it is vital to improve cryocooler performance. In this project, SHI developed a high-efficiency Stirling cryocooler and performance tests were conducted. As a result, a cooling capacity of 151 W at 70 K with a compressor input power of 2.15 kW corresponding to a COP of 0.07, was achieved. Actual vehicle testing was also conducted. The results of tests and simulations showed that it is possible to increase efficiency about 10% compared to a conventional electric motor.

Multidisciplinary analysis of the transient performance of a 20 kW class HTS induction/synchronous motor cooled with a cryocooler and gaseous air-gap coolant

“…This motor has been mounted on a middle class passenger car, and an actual running test has been successfully performed. In addition, researchers at Sumitomo Heavy Industries, Ltd. (Japan) have developed a Stirling cryocooler for an HTS electric bus [15]. The reported cooling power and coefficient of performance (COP) are, respectively, 151 W and 0.07 at 70 K. The present authors' group (at Kyoto University, with collaborators) (Japan) has been developing a 20 kW class HTS induction/synchronous motor (HTS-ISM) for transportation equipment such as buses, trucks, and middle class car [16].…”