Ferrite Core Magnetothermal Equilibrium Design for Wireless Power Transfer Systems Using a Novel Differential Regulation Coil

The safe operation and durability of a wireless power transfer (WPT) system are challenged as the power level increases due to the uneven magnetothermal distribution in the ferrite core. However, existing research has rarely taken this issue into consideration. In this paper, a novel differential regulation (DR) coil is designed and installed in the magnetic coupled structure (MCS) to achieve a uniform magnetothermal distribution of the ferrite core. To provide a theoretical foundation for the DR coil design and to evaluate the effectiveness of the proposed magnetothermal equilibrium design, a comprehensive magnetothermal equilibrium formula (MEF) is given. An 11.1 kW/85 kHz experimental prototype is built to validate the magnetothermal equilibrium method. Results show that utilizing the proposed DR coil, the maximum temperature of ferrite core and the leakage flux can be reduced by 20.0% and 18.2%, respectively. Moreover, the spatial distribution uniformity of the temperature on the ferrite core can be improved by 56.3%, and the uniformity of the spatial distribution of the magnetic flux density can be improved by 10.7%. Overall, the magnetothermal equilibrium of ferrite cores has increased by 28.1%.