Investigation on the stability evaluation of multi-strand superconducting cable related with ramp-rate limitation

This paper describes stability of CICC superconducting magnets related with RRL (Ramp-Rate Limitations). Although RRL is known as a significant obstacle for successful operation of field-varying AC superconducting magnets, its precise investigation is difficult due to complex unknown parameters and difficulties of experimental measurements. To investigate RRL for practical multi-strand CICC, a simplified analysis model is suggested with some reasonable assumptions. This model considers accurate current diffusion phenomenon inside CICC and realistic transient convection heat transfer by supercritical helium. Parametric study is also performed with the analysis model to investigate the effect of the strand parameters. Summarizing the quench recovery or cable quench result after a local quench for given simulation parameters, a new stability evaluation method is suggested and it can give some design criterion by guaranteeing the stable operation regime of superconducting magnets. The new evaluation method, which is called 'RRL quench recovery map', is applied to the previous experimental results and it shows that this map can be used as a design criterion for practical superconducting magnets. (c) 2007 Elsevier B.V. All rights reserved.