Design and performance of A 5 kJ HTS μ-SMES

A Bi-2223 magnet has been constructed by American Superconductor for a 5 kJ micro-SMES system at Tampere University of Technology. The nominal energy of the magnet was obtained by 160 A magnet current. The magnet was cooled to the operating temperature of 20 K with a two stage Gifford-McMahon type cryocooler with a cooling power of 8 W at 20 K. The HTS micro-SMES was tested in an uninterruptible power supply application, where the SMES supplies power for a load during a break in mains. In this paper the design of the magnet and the cryogenic system as well as test results are presented and discussed together with problems related to the cryointegration of the magnet.