When there are non-ferromagnetic metal objects around the power transmission channel of magnetic resonance coupling wireless power transmission systems

the power transmission performance will be affected by the interaction of the alternating magnetic field with metal objects. For this problem

a non-contact power transmission system model considering the influence of metal objects is developed

and mathematical expressions of transmission power and efficiency in an arbitrary status are deduced. The influence laws of metal objects on the transmission performance are analyzed by means of theoretical analysis and experiment. The results show that resonance systems influenced by non-ferromagnetic metal objects contain the basic characteristics of what an ideal system has

such as resonance frequency splitting

the optimum operating frequencies of power or efficiency often are not the same. Furthermore

the presence of metal objects can also cause resonance frequency shifting upward relative to the original system

and metal objects around the transmission channel do not always have a negative impact on the transmission performance

for it may benefit the transmission power or efficiency in the weak coupling condition. Theoretical analysis indicates that the root cause of the transmission performance change is that the eddy current parameters will result in variations in the system equivalent parameters

including equivalent impedance of system and load. Experimental results are in good agreement with the theoretical analysis conclusions. This work is supported by National Natural Science Foundation of China (No. 61403201)

Chinese PLA Pre-research Foundation of China (No. 9140A05020114BQ02063)

and Fundamental Research Funds for the Central Universities (No. 30915118824).