| The wireless power transfer system has the advantages of convenience,safety,versatility and avoiding structural damage.The most important thing is to use this technology to realize dynamic charging,which has great economic and social benefits.When the wireless energy transmission system is in operation,there is a large amount of alternating electromagnetic field around the coupling mechanism.If the energy is not fully applied,the surrounding equipment and organisms will be exposed to a strong magnetic field,causing serious harm.Therefore,the research and experimental analysis prove that the use of magnetic shielding materials can not only effectively solve this problem,but also improve the transmission efficiency of the wireless energy transmission system.In this dissertation,the mathematical model analysis of the string-string resonant wireless power transfer system is used to obtain the factors affecting the transmission characteristics of the system,including load,mutual inductance and frequency.On this basis,the influence of magnetic shielding on the parameters of the coupling mechanism and the transmission efficiency of the wireless power transfer system is analyzed.Through the simplification of the string-string type wireless power transfer system parameters,when the load resistance value is constant,the influence of mutual inductance and detuning factor on the transmission characteristics of the system is derived,and the conditions for the system to generate frequency split are obtained.At the same time,the influence of mutual inductance and frequency on the transmission characteristics of the system is analyzed by the control variable method.The influence of the mutual inductance of the coupling mechanism on the optimal load of the system and the inductance on the quality factor of the primary and secondary circuits is studied.Finally,the influence of the resonance state of the primary and secondary loops on the transmission efficiency of the system is analyzed.The loss of the wire at high frequencies is analyzed by Maxwell,which is mainly caused by the skin effect and the proximity effect.The 3D model of the coupling mechanism is established by Maxwell,and the inductance,mutual inductance and transmission efficiency of the wireless energy transmission system before and after the magnetic shielding of the coupling mechanism are calculated.The main reason for the detuning of the wireless energy transmission system after the introduction of the magnetic shielding material into the coupling coil is analyzed,and the system detuning problem is solved by modifying the compensation resonant capacitor.The transmission line theory is used to analyze the shielding effectiveness of the uniform shielding material.The larger the wheelbase of the coupling coil,the greater the shielding effectiveness.Although the magnetic shielding does not significantly improve the transmission efficiency of the system in the strong coupling state,it can effectively reduce the magnetic field strength outside the coupling mechanism.By comparing and selecting the topology and key components of the resonant wireless power transfer system,a hardware circuit is built.The device is used to verify that the magnetic shielding will cause the system to be detuned.Correcting the compensation capacitor can improve the transmission efficiency of the system. |
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