Analytical expressions for maximum transferred power in wireless power transfer systems

In this paper, we present the analytical expressions of the resonant peaks of input impedance and the frequencies of maximum transferred power in the wireless power transfer systems in case of tight magnetic coupling. The analytical expressions predict the frequencies of power source where the maximum power is transferred in both cases of the constant AC voltage source and the constant AC current source. We prove that the resonant frequencies of the input impedance in the wireless power transfer systems coincide with the frequencies at which the transferred power is maximized for the constant AC voltage source and the constant AC current source. The test vehicles of the coupled rectangular coils are simulated with 3D EM solver and fabricated on printed circuit boards. Experimentally, it is verified that the analytical expressions predict the changes in the resonant peaks of input impedance of the wireless power transfer systems, its relationship with frequencies of maximum transferred power and their dependency with the source type in the wireless power transfer systems.