Analysis of Turn-to-Turn Contact Resistance Characteristics of Metal Insulators for Contact Resistance Control of Superconducting Coils

In high-temperature superconducting (HTS) coils, maximizing current density and achieving high magnetic fields often relies on no-insulation (NI) winding techniques. While this approach is beneficial for compact coil design and magnetic field stability, it can lead to magnetic field charging delays due to the absence of insulation between turns, which allows unwanted currents to form and interfere with magnetic field performance. This study aims to mitigate such delays by investigating the turn-to-turn contact resistance characteristics when using metal insulators between coil turns, focusing specifically on mesh structures as controllable insulating layers. Experiments were conducted under liquid nitrogen conditions, simulating the superconducting environment, where we measured contact resistance across different mesg and pressures to understand the relationship between these variables and their effect on current distribution between coil turns. The results show that the contact resistance increases with the mesh count, reaching a peak at 300 mesh STS 304, after which the mesh density becomes too fine and the contact resistance decreases. Similarly, increasing applied pressure significantly reduced contact resistance, with the effect becoming pronounced at pressures above 15 MPa due to increased a-spot connections between surfaces. These findings offer insights into optimizing HTS coil performance for applications requiring high-speed charging and discharging.