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.
Abstract. For wide spread high-temperature superconductor (HTS) devices, a cryocooler having COP of >0.1, with a compact size, light weight, high efficiency and high reliability is required. For practical use of superconductive devices, Sumitomo Heavy Industries, Ltd. (SHI) developed a high-efficiency Stirling type pulse tube cryocooler (STPC). The STPC had high reliability and low vibration. However, its efficiency was not enough to meet the demands of an HTS motor. To further improve the efficiency, we reconsidered the expander of cryocooler and developed a Stirling cryocooler (STC). Two prototype units of a compact, high-efficiency split Stirling cryocooler were designed, built and tested. With the second prototype unit, a cooling capacity of 151 W at 70 K and a minimum temperature of 33 K have been achieved with a compressor input power of 2.15 kW. Accordingly, COP of about 0.07 has been achieved. The detailed design of the prototype units and the experimental results will be reported in this paper.
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