Development of superconducting magnet with low electric power loss for SMES

A superconducting magnet with a 0.01% electric power loss was developed. This magnet is used to store electric power as magnetic energy and to stabilize an electric power system. This magnet of 78-cm outer diameter and 27-cm width consists of 18 double-pancake-type coils and was designed with a 10-T/s pulse-discharge speed and 350-A transportation current. To reduce energy loss caused by the eddy current, the copper wire stabilizer surrounding the superconducting material was subdivided by a cupronickel layer. To prevent quench, cooling channels were arranged between pancakes of the magnet and between turns of the coil. Elementary analysis and tests of mechanical strength, insulation, cooling and quench were performed, and the performance of this magnet was confirmed with high-speed charge-discharge tests and forced-deenergizing tests. >