A Thermally Reliable Variable-Topology Magnetic Coupler with Closed-Loop Multiphysics Co-Design for Guided-Platform AUV Wireless Charging

Guided-platform wireless charging enables persistent autonomous underwater vehicle (AUV) operation but imposes severe electromagnetic and thermal constraints due to large docking gaps, full-angle misalignment, and compact subsea integration. This paper proposes a thermally reliable variable-topology magnetic coupler (VTMC) with a radially reconfigurable transmitter and a staggered dual-layer receiver to ensure strong coupling and rotation tolerance. A temperature-aware hybrid loss model, combining analytical formulations with finite-element field extraction, is developed to accurately capture high-frequency and temperature-dependent losses. These spatially nonuniform losses are embedded into a loss-validated closed-loop multiphysics framework, which identifies the receiver nanocrystalline core as the dominant hotspot source and reveals the underlying thermal mechanism. Based on this insight, a physics-guided stacked-core optimization is proposed to reduce peak temperature and improve thermal uniformity without degrading electromagnetic performance. A 4.2 kW prototype validates the proposed approach, achieving 92.8% DC–DC efficiency, stable power transfer over 0–360° rotation, and robust operation under both resistive-load and constant-voltage charging conditions. The optimized design demonstrates repeatable hotspot mitigation, reducing the measured peak core temperature from 48.5 °C to 45.1 °C.