Speaker
Description
No-insulation (NI) high temperature superconductor (HTS) coils are characterized by their turn-to-turn contact resistivity, leading to circuit-based models composed primarily of resistors and inductors. In a simplified lumped circuit representation, NI HTS coils can be modeled as variations of RL circuits, yielding voltage responses governed by a single-valued time constant. However, experimental measurements tend to deviate from these simplified predictions.
To achieve improved accuracy, two key factors can be considered: (1) the distributed nature of the time constants rather than relying on a single-valued parameter, and (2) the changes in coil inductance caused by screening currents. In this study, we demonstrate how to extend the standard RL-circuit transfer function to accommodate continuously distributed time constants. In addition, we employ the Preisach model of hysteresis to incorporate inductance hysteresis effects, thereby capturing the impact of screening currents on coil voltage responses.
Although these refinements introduce additional complexity, simulations based on these enhanced models retain computational efficiency comparable to that of conventional lumped circuit approaches. Consequently, the refined models can enhance the reliability of NI HTS coil performance assessments, including more accurate estimates of turn-to-turn contact resistivity.
