Evaluation of power transfer efficiency with ferrite sheets in WPT system

Proper selection of magnetic material is very important to maximize the power transfer efficiency (PTE) in case of the conductor in the receiving coil. The effects of the relative permeability and loss tangent of the magnetic material are investigated. A relatively low complex permeability ensures a high efficiency in wireless power transfer system (WPT) at 6.78 MHz. To maximize the PTE, the properties of the selected ferrite sheet should include a relative permeability higher than 200, a thickness of 600 um, and a loss tangent less than 0.01. Although 2-layer ferrite sheets show lower PTE than those of complex of complex of ferrite sheets, they have relatively high permeabilities and low core losses, which are beneficial in e real environments.