Design of a rectangular coil for an effective magnetic resonance wireless power transfer system

The design method of a rectangular spiral coil with circular cross section is presented for an effective wireless power transfer system based on magnetic resonance in the MHz frequency. The main idea is to calculate ac resistance and inductance of the coil by using volume filament model. In calculation, its equivalent circuit is proposed and both skin and proximity effects are considered. By using the proposed calculation method, a compact coil can be optimized for maximum power transfer efficiency. The calculation results and optimization method are verified with experiment by fabricating and measuring a wireless power transfer system with two planar rectangular multi-loops resonant coils.