Investigating the effect of transverse compressive loads on the electromagnetic performance of superconducting CORC® cables

Abstract

High-temperature superconductor (Re)Ba2Cu3O x (ReBCO) conductor on round core cable (CORC®) has a large current carrying capacity for high field magnets. Lorentz forces acting on CORC conductors, cause a reduction of the critical current, or even permanent degradation of their performance when exceeding critical values. Transverse compressive stress is one of the principal mechanical stresses when CORC cables are bundled to cable-in-conduit conductors (CICC) conductors capable of operating at currents up to 100 kA in magnetic fields of up to 20 T. In this research, a mechanical-electromagnetic model is developed to study the effect of transverse compressive loads on the electromagnetic performance of CORC cables. A mechanical transverse load on the cable is implemented to simulate the electromagnetic force. A comparison of numerical simulations with experiments for a three-layer CORC cable is first performed to validate the model’s reliability, with particular attention to critical current reduction during the transverse compression process. A novel feature of this paper is that the model developed can analyze both mechanical response under transverse compressive loads and electromagnetic performance under applied AC magnetic fields with low amplitudes. On this basis, the model investigates the effects of winding parameters on the axial strain and critical current reduction of the ReBCO layer in a single-layer CORC cable. The numerical analysis shows that increasing the winding angle can reduce the axial strain and critical current reduction of the ReBCO layer in the contact area. Subsequently, a detailed comparative study is carried out studying the axial strain of the ReBCO layer in the non-contact area with and without taking the winding core into account. In addition, a sudden increase in the magnetization loss is explained when the transverse compressive load reaches a certain level. Finally, a six-layer CORC cable’s electromagnetic analysis is performed, and each tape layer’s critical current reduction is investigated and discussed. The comparison of magnetization loss and current density between six- and single-layer CORC cables in the no-strain case is also given. This finite element model can guide optimizing a cable design for specific application conditions.