The discovery of high temperature oxide superconductors has stimulated us much interest in superconductivity applications to electric machines and apparatus again. Focused on the feasibility of such superconductors for electric rotating machines or motors, here are discussed perspectives and features of many sorts of electric motors such as to be available at present.
The Japan Atomic Energy Research Institute (JAERI) is conducting Demonstration Poloidal Coil (DPC) program for investigation of superconducting pulsed-coil technology for fusion. The DPC cryogenic system is designed to cool three forced-cooled superconducting coils being fabricated in this program and the system is composed of newly developed cryogenic circulation pump, cold compressor, and vapor-cooled current leads. The installation of these componets was completed in December of 1987 and the performance test of the whole system was carried out in March, 1988. In this test, we have demonstrated that the cryogenic system meets the specifications for cooling the coil system.
A new compact cryogenic cold compressor was developed by Japan Atomic Energy Research Institute (JAERI) in collaboration with Isikawajima-Harima Heavy Industries Co., Ltd. (IHI) in order to produce the supercritical helium below 4.2K for Demonstration Poloidal Coils (DPC) which are forced-flow cooled type superconducting pulse coils. This compressor is one of key components for DPC test facility. The cold compressor reduces pressure in liquid helium bath, which contains liquid helium of around 3, 000l, down to 0.5atm efficiently. Consequently, supercritical helium down to 3.5K is produced and supplied to the DPC coils. A centrifugal compressor with dynamic gas bearing is selected as a compressor mechanism to realize high adiabatic efficiency and large flow rate. In this performance tests, the compressor was operated for 220h at saturated condition from 0.5 to 1.0atm without any failure. High adiabatic efficiency (more than 60%) is achieved with wide flow range (25-65g/s) and the design value is fully satisfied. The compressor can rotate up to 80, 000rpm at maximum then the coil supply temperature of supercritical helium is 3.5K.