| Wireless charging has attracted the attention of scholars from all over the world because of its advantages such as non-contact spark,adaptability to severe weather,low wear rate of equipment and so on.It is suitable for electric vehicles,automatic machinery and equipment,unmanned guided vehicles and other application scenarios.With the development of research on wireless power transfer,people put forward higher requirements on the transmission efficiency of wireless power transfer system and the safety of electromagnetic radiation.Magnetic coupler plays an important role in the energy conversion process of radio energy transmission system,so it is necessary to optimize the design of magnetic coupler.In this paper,based on the discussion of ferrite monolayer shielding magnetic coupler and ferrite and aluminum plate as double shielding magnetic coupler,a composite shielding magnetic coupler composed of ferrite,nanocrystalline and aluminum foil is proposed.Firstly,this paper analyzes the basic principle of wireless power transfer system,and models the PS compensation ICPT system.The principle of electromagnetic shielding and the application of shielding materials are analyzed.The magnetic field distribution of planar helical coils was studied by JMAG finite element simulation.The magnetic circuit model was established and the coupling coefficient expression was derived.The shielding principle of high conductivity material is analyzed,the equivalent circuit model diagram of asymmetric radio energy transmission system after aluminum plate is added is established,and the formula of the influence of aluminum plate shielding on wireless charging system is deduced,which provides a theoretical basis for the design of composite shielding structure.Secondly,this paper takes PS compensated ICPT system as the research object,establishes the finite element copy model of ferrite monolayer shielding structure,and analyzes the characteristics of the magnetic field around the magnetic coupler of ferrite monolayer shielding structure.Aiming at the deficiency of single layer shielding structure in shielding effect,the double layer shielding structure of ferrite and aluminum plate was studied.The double-layer shielding structure combines the advantages of soft magnetic material and high conductivity material,which reduces the shielding effect below the safety standard.However,due to the presence of aluminum plate,the coupling coefficient is reduced and the system efficiency is reduced.Considering the advantages and disadvantages of the above shielding structures,a composite shielding structure composed of ferrite,nanocrystals and aluminum foil was proposed,and a field model was established to provide a theoretical basis for magnetic field analysis.The three shielding structures were compared and analyzed.The results show that the magnetic coupler with composite shielding structure has better shielding effect,the coupling between coils is stronger than that with double shielding structure,and it is lighter in weight,lower in cost and more flexible.Finally,the magnetic coupler with composite structure was applied to the wireless charging system of the induction cook-fruit and vegetable machine,and the Saber circuit simulation and experimental design were passed.The coil parameters of the magnetic coupler with the composite shielding structure and the single-layer and double-layer shielding magnetic coupler were verified through experiments,and the correctness of the simulation results were proved.Finally,the magnetic coupler with the composite shielding structure was verified by the experimental electricity,and the experimental results proved the correctness and practicability of the design of the composite shielding structure. |
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