Research on discharged unsteady response of straight CORC based on the equivalent circuit model

Abstract

CORC (Conductor on Round Core) is considered one of the most promising superconducting cable/conductor structures for large-scale applications particularly in fusion magnets, owing to its stable mechanical structure, high current-carrying density, and low AC losses. The utilization of an equivalent circuit model has been instrumental in studying the current distribution within HTS conductors. In the traditional CORC equivalent circuit model, the equivalent inductances are typically set at fixed values. However, given that monitoring current distribution within the tape and between layers is crucial, assessing whether changes in contact resistance could lead to alterations in overall inductance and whether radial currents might cause irreversible damage to the conductor during operation becomes imperative. This study has developed an equivalent circuit model based on a CORC-like structure, starting from a simple straight CORC conductor, and its accuracy has been validated. Through this model, the inductance value of a complex multi-layer CORC configuration has been calculated. When the charging current exceeds 0.7I_c, the inductance of the non-insulating CORC experiences a sudden change. By examining variations in inductance values, it is possible to infer the presence of interlayer currents within the CORC during transient responses. Furthermore, discussions encompass the current flow direction and trends of different CORC specifications during on–off current scenarios, exploring whether current transmission occurs in non-superconducting layers when the CORC is subjected to high currents, determining potential abrupt changes in overall inductance, and assessing the risk of conductor damage during discharge.