A simple protection evaluation method for no-insulation REBCO pancake coils during local normal-state transition

Abstract No-insulation (NI) and metal-insulation (MI) winding techniques are promising for enhancing the thermal stability of REBCO pancake coils, toward the practical use of nuclear magnetic resonance and magnetic resonance imaging systems. The NI and MI REBCO pancake coils showed high thermal stability in many over-current tests. However, a disadvantage is a charging delay due to low turn-to-turn contact resistance. Therefore, many researchers have tried to increase turn-to-turn contact resistance to overcome the charging delay problem. Meanwhile, a partial element equivalent circuit (PEEC) model can accurately simulate the over-current and charging/discharging tests of NI REBCO pancake coils in detail. Using the PEEC model coupling with thermal finite element analysis (FEA), the thermal stability was evaluated during a local normal-state transition. From the simulation results, it was…