Electro-Thermal Analysis and Optimization of Wireless Power Transfer Coupler for Rotary Steerable Systems

In rotary steerable systems, stable coupling and effective thermal management of the wireless power transfer (WPT) magnetic coupler during rotation are critical to reliable system operation. An unstable coupling coefficient can degrade power transfer efficiency, while uncontrolled losses may lead to thermal failure and compromise system stability. To address these issues, this paper proposes a dual-solenoid-Q-type rotary magnetic coupler suitable for rotary steerable tools and systematically analyzes and optimizes its heat generation and heat dissipation characteristics. The proposed magnetic coupler maintains a stable coupling coefficient throughout the rotation process without requiring complex winding schemes or coil configurations. To reduce heat source losses, the effects of coil turns, receiver opening angle, and coil height on heat generation are investigated in detail. Furthermore, a coupled heat dissipation model is established to comprehensively evaluate the combined effects of six key structural parameters, including coil height spacing, transmitter and receiver turns, transmitter and receiver turn spacing, and receiver opening angle, on the average temperature and total loss of the magnetic coupler. Based on the optimized parameters, a 500 W WPT simulation model with an LCC-S compensation topology is established. The results show that the proposed optimization method effectively reduces system losses, with the total system loss remaining below 40 W. The maximum temperature rise is significantly reduced to 17 °C, corresponding to a reduction of more than 43%. These results demonstrate that the proposed method effectively suppresses the risk of overheating under extreme downhole operating conditions and improves the operational reliability of the WPT system.