Multi-physics quench simulation of no-insulation HTS insert coils with high background magnetic field

Abstract

Compared with traditional insulated High Temperature Superconducting (HTS) coil, no-insulation (NI) HTS coil has higher thermal stability and self-protection capability, so that is considered as an important way to generate high steady-state magnetic field. This paper focuses on the experimental phenomena that mechanical damage always occurs in NI coils during quench with high background field. A multi-physics quench simulation model is established for NI insert coils, which contains a 2-d axisymmetric partial element equivalent circuit (PEEC) model for electromagnetic calculation and two axisymmetric finite element models for thermal and mechanical analysis. Based on these models, we analyzed the electromagnetic, thermal and mechanical phenomena of insert coils during quench propagation and recovery. The simulation results show that mechanical damage may occur in the outer superconducting zone near the normal zone in no-insulation coils during quench, and thermal strain caused by temperature rise during quench may exacerbate mechanical damage. Meanwhile, quench at different single-pancake coils has different effects on the mechanical performance of the entire insert coils. Based on the electromagnetic simulation results, we also analyzed the time delay of the traditional terminal voltage quench detection method and its causes. This study analyzed the multi-physics quench phenomenon of no-insulation HTS insert coils. And the results imply that hoop strain will increase to the critical strain due to high magnetic field and current redistribution caused by radial current shunt during quench, resulting in mechanical damage. Additionally, radial current shunt and induced voltage will retard quench propagation velocity, resulting in the time delay in terminal voltage quench detection.