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This work presents a modified lumped-circuit model for a saddle-shaped no-insulation (NI) high temperature superconductor (HTS) coil in overcurrent, which is defined by the situation that azimuthal current is close to or greater than the critical current. We suggested the variation of the coil's circuit parameters, such as inductance, ‘index’ resistance, and characteristic resistance. We modified the base assumptions of the conventional lumped-circuit model and experimented to validate the suggested model. An 82-turn saddle-shaped NI coil was fabricated, and terminal voltage and magnetic field were measured during the overcurrent test in a 77 K liquid nitrogen bath. Compared to the conventional model, our modified lumped-circuit model reduced the error between measurement and simulation from 44.2% to 2.9%. We inversely calculated the variation of circuit parameters and magnet constant, which cannot be the constant value, and the results are presented.

This study investigated the thermal and electrical characteristics of a high-temperature superconducting motor intended for electric vehicle traction. Particular attention was paid to mitigating the temperature increase induced by eddy currents in the aluminum bobbins and to increasing the operating time while maintaining the critical current margin. Adjustments were made to incorporate multiple axial segments composed of anodized aluminum, thereby establishing segmented eddy current loops. Models ranging from two to 40 segments were investigated at the maximum power of 300 kW for the motor. It was observed that the implementation of a 40-segment bobbin reduced the eddy current losses by approximately 78%. A marked decline in the temperature rise was realized, considerably extending the operational time of the motor. The operational time increased from an initial 7 seconds at maximum power to 221 seconds, attributed to the reduced eddy current losses and the resulting decrease in temperature rise.

This work presents a distributed-circuit model for analyzing experimental results of fast-ramping behaviors of a saddle-shaped REBCO dipole magnet wound with a bundled conductor. Terminal voltage and center magnetic field were measured during the test performed at 77 K temperature. Our distributed-circuit model accurately reproduced the observed electromagnetic behaviors, demonstrating its validity for the fast-ramping operation of an HTS magnet. We also analyzed the current discrepancy between bundled conductors and Joule dissipation due to the various ranges of contact resistivity.