Abstract
A Nb3Sn supercouducting magnet to be stored 400 kJ was developed as a unit magnet for 2.4 MJ-SMES system used for stabilization studies of electrical power systems. The superconducting magnet consists of a cryostat and a Nb3Sn coil, the dimensions of the coil is 340 mm inner diameter, 700 mm outer diameter and 177 mm axial length. The pool cooled coil is a stacked up of twenty Nb3Sn double pancakes, and the cooling channels are aligned between pancake coils. To reduce Joule loss in electrical power converters, the maximum operating current of the coil is designed to be 350 A which is one order less than the operating currents of other same scale coils for pulse use. Conductor is Nb, Sn monolithic conductor of which cross section is 1.50×2.38mm2. For good superconducting stability and high dielectric strength of the coil, the Nb3Sn double pancakes were wound by react-and-wind technique.
Operation of DC current to 105% (367.5 A) of the design operating current was achieved without quench. After the whole of the coil exposed out of liquid helium, the coil did not quench under 120 A current operation during over 2 hours. It was verified that the coil was stable for the SMES system.
