Selection of Ferrite Depending on Permeability and Weight to Enhance Power Transfer Efficiency in Low-Power Wireless Power Transfer Systems

With advancements in the field of electrical engineering, various low-power portable electronic devices have been commercialized. To eliminate and unify different types of cables, inductive wireless power transfer (WPT) technology, which uses magnetic fields to transfer energy, is being applied in numerous applications. Low-power devices typically have small coils and loads, leading to low power transfer efficiency even over short distances. Magnetic materials such as ferrites are used to improve power transfer efficiency (PTE). It is well known that high-permeability ferrites with low magnetic reluctance are ideal for achieving strong magnetic coupling. However, continuous increases in permeability raise the cost and weight of the ferrite, making it necessary to select ferrites with appropriate permeability from a mass-production perspective. This paper models and analyzes the changes in mutual inductance and power transfer efficiency with varying ferrite permeabilities using magnetic circuits, providing guidelines for the selection of suitable ferrites considering efficiency improvements. The proposed method is validated through 3D electromagnetic simulations and experiments, showing a power transfer efficiency difference of up to 0.6% between the experimental and calculated results.