Structural Determinant of Electromagnetic Response in Closed-Loop HTS Coils Under Traveling Magnetic Fields: Switching from Demagnetization to Magnetization via Outermost Tape Reconfiguration

Abstract

In applications such as maglev trains, onboard high-temperature superconducting (HTS) magnets are exposed to traveling magnetic fields, often leading to coil current decay (demagnetization). Conversely, traveling magnetic fields are employed in HTS flux pumps for contactless charging (magnetization). To clarify the underlying mechanisms and transition conditions between these two opposing phenomena, this paper investigates the influence of the outermost tape configuration on the electromagnetic response of a closed-loop HTS coil under a traveling magnetic field via finite element modeling. The study demonstrates that rotating the outermost half-turn tape of the closed-loop coil by 90°, orienting its surface perpendicular to the traveling magnetic field, transforms it into an effective embedded magnetization source capable of generating a net DC magnetization voltage. When this magnetization voltage exceeds the demagnetization voltage arising from the dynamic resistance effect in the main coil body, the coil exhibits net magnetization; otherwise, it exhibits net demagnetization. Parametric studies further reveal that by strategically designing the configuration of the outermost tape, the direction and magnitude of this net effect can be actively controlled, enabling proactive management of the coil’s dynamic behavior under the traveling magnetic field. This study identifies the coil’s own configuration as the key factor governing its interaction mode with traveling magnetic fields, providing a novel structural design concept for developing onboard HTS magnets with high interference immunity.