2 MJ SMES for an uninterruptible power supply

A low temperature 2 MJ SMES is being built for an uninterruptible power supply. The superconducting magnet is designed for a carry over time of 8 s at a mean power of 200 kW. The maximum power of the SMES is 800 kW at an operating current of 1 kA. The magnet is being built as a liquid helium bath cooled solenoid. The cryogenic system is designed for no boil-off operation and cryocoolers are used for recondensation of the evaporated helium. Low cryogenic losses are achieved by the use of HTS-current leads, AC losses of the magnet are reduced by using a mixed matrix Cu/CuNi/NbTi superconductor. The SMES is connected to the power electronic of the UPS by a chopper circuit and a DC link capacitor. This paper describes the system design and focuses on the superconducting magnet.