Design, manufacturing and cold test of a superconducting coil and its cryostat for SMES applications

This paper describes the design and manufacturing of a 25 kJ superconducting coil as well as its cryostat and magnet support, including current leads and cryogenic services, for an SMES. The coil design is based on a minimum volume criteria. The cryostat is designed for 60 l of liquid helium, and the magnet support with current leads optimised for 150 A. Using numerical modelling, the total heat transfer into the liquid is calculated and minimised. The manufacturing of both components is also presented, as well as the complete system operation. Finally the paper presents the power converter topology that is controlled in optimal PWM mode with a low switching frequency. In order to compensate different power oscillations, the power converter quickly interchanges adjustable and uncoupled levels of real and reactive power.