Research On Coil Magnetic Shielding Of High Power Wireless Charging Device On EVs

Magnetic coupling resonant wireless power transfer technology has the advantages of convenience,fast,safety,and a high degree of automation,and it has a good application prospect in the field of electric vehicles.The electromagnetic safety problem has restricted the practical application of this technology in the field of electric vehicles,and the magnetic shielding structure is the main measure to solve this problem at present.However,the improvement of the shielding effect of the magnetic shielding structure means an increase in cost and weight,and even affects the power transmission capacity and efficiency of the system.In order to reduce the weight of the magnetic shielding structure and control the cost,it is necessary to research and optimize the magnetic shielding structure of the magnetic coupling resonance wireless energy transmission technology in practical applications.In addition,the anti-offset and anti-rotation characteristics of the coupling mechanism are also studied in this paper.First,because of the resonance compensation network plays a decisive role in the input and output characteristics of magnetically coupled resonant wireless energy transmission technology,this paper analyzes the working mechanism of the double LCC type resonance compensation network with excellent input and output characteristics and derives its parameter calculation equations.An accurate circuit simulation model is established to help accurately analyze the performance of magnetically coupled resonant wireless power transfer systems and then accurately calculate their electromagnetic fields.Then,a three-dimensional finite element simulation model of the coupled coil is established using the finite element electromagnetic simulation software,and the influence of ferrite parameters and metal plate parameters on the coil parameters,the degree of coupling of the coils,the system performance,and the magnetic shielding effect is studied and analyzed.The ferrite parameters that are studied include the ferrite permeability and thickness,and the metal plate parameters that are studied include the metal plate material and the metal plate thickness.Secondly,based on the three-dimensional finite element simulation model of the coupling coils,the influence of the relative position and angle of the coupling coils on the parameters of the coupling coils and the degree of coupling of the coils were analyzed.With the same input voltage,the changing rules of the system power transfer capacity,the system power transfer efficiency and the shielding effect of the magnetic shielding structure are analyzed.It is found that the parameters of the coupling coil and the system performance are very sensitive to the vertical distance between the coupling coils,and the horizontal offset and relative angle changes within a certain range have very limited effects on the coil parameters and system performance.At the same input voltage and load state,magnetic field radiation is still safe.Finally,in view of the weight of the metal plate of the coupling coil,this paper proposes an optimized design of a metal plate with a groove.The grooved optimized design uses a thicker metal plate in the place where the magnetic field distribution is concentrated and uses a thinner metal plate in the place where the magnetic field distribution is sparse.While maintaining the original shielding effect of the magnetic shielding mechanism,it reduces the weight of the metal plate at the back of the coupling coil is 27.36%,which reduces the material cost,which is beneficial to the lightweight design of the magnetic shielding mechanism and the lightweight application of the magnetic coupling resonance wireless power transfer technology.