Investigation of heat transfer effect on ramp-rate limitation of superconducting cable

Ramp-rate limitation, which is known as a serious obstacle for fast charging of a superconducting magnet, is investigated by an experiment with a two-strand sample conductor and numerical analysis. During the experiment, typical ramp-rate limitation results were observed. The sample showed quench recovery by current redistribution or irreversible 'cable quench' according to the operation conditions. To investigate the recovery or quench criterion, numerical analysis is performed considering both electro-magnetic and thermal interaction. The simulation results show that the status of the low-current strands determines 'recovery' or 'cable quench' when the 'local quench' first occurs at the high-current strand. From the analysis, heat transfer conditions such as boiling heat transfer and contact heat transfer between the strands as well as current nonuniformity are the most governing factors for the stability criterion. Therefore, it is possible to propose a stability criterion for the ramp-rate limitation according to the operation condition of the superconducting magnet. Moreover, the effect of heat transfer conditions to overcome the ramp-rate limitation for the given operation conditions is investigated quantitatively.