Influences of WPT-Coil Losses and Coupling Coefficient on the Resonance Circuits of Wireless Power Transfer Systems

Wireless Power Transfer (WPT) systems for electric vehicles transfer energy by magnetic field between two resonance circuits. The topology of the resonance circuits can be either a series or a parallel circuit of a large coil and several capacitors. Coil wire resistance causes ohmic losses which affect resonance frequency as well as efficiency. These influences have been investigated in dependency of the coupling factor between both coils. A series compensation is shown to reduce the influence of the coupling on the resonance frequency.