Design And Optimization Of Magnetic Coupler For Wireless Charging System

Compared to wired charging,wireless charging has advantages of convenient to operate,no contact sparking,adaptability to harsh environments,much more intelligent,etc.Wireless charging can swim with the automation,unmanned development trends of electrical equipment like electric vehicles and robots,and is considered as an inevitable trend of future charging methods.Although the wireless charging technology has been receiving great attention,the large and medium power wireless charging systems used in electric vehicles,robots,and other devices are not mature yet.The efficiency still needs to be improved,and radiation and other security issues remain to be solved.Magnetic coupler is the key component of the energy conversion and transmission for wireless charging system.The design and optimization of magnetic coupler are directly related to the output power,efficiency and radiation level of the wirelesscharging system.In this paper,the design and optimization of the magnetic coupler are given in three aspects:optimization of coil parameters of the magnetic coupler,design and optimization of the magnetic core structure,shielding structure design.Through the above three aspects,the efficiency of the wireless charging system is improved and the radiation is reduced.In this paper,the basic theory of wireless charging system is analyzed,and then the expressions of the output power and efficiency for wireless charging system under non-resonance conditions are derived.Then,the relationships between output power and frequency,efficiency and frequency are plotted using MATLAB programming,and the conditions for frequency splitting in the system are given.By studying the critical condition of frequency splitting,a solution of frequency splitting is proposed.That is,the frequency splitting can be avoided by designing the coil inductance of the magnetic coupler reasonably.On the basis of above,the expressions of critical inductances for the transmitting coil and the receiving coil are given respectively,and in order to avoid frequency splitting,a flow chart for determining the coil inductances is given.The magnetic field distribution of circular coils and DD coils is studied by using ANSYS Maxwell simulation.According to the distribution of the magnetic field,the self-coupling regions and the mutual-coupling regions are divided,and the magnetic circuit models are established.The coupling coefficient expressions of the circular coil and the DD coil are derived.Based on the parameters affecting the coupling of the coil shown by the coupling coefficient expressions,these parameters are optimized by designing the magnetic core structure in the 3D simulation,then the mutual-coupling between the coils is enhanced,and the self-coupling of the coils is weakened,thereby coupling coefficients of coils are improved.The wheel-shaped magnetic core structure for circular coil and the concave-shaped core structure for DD coil are designed,and the advantages of the two core structures are verified by 3D simulation.On the basis above,a universal flow chart of design and optimization magnetic core structure is proposed,which provides the basis for the magnetic core structure of different kinds of magnetic couplers.The shielding principle of high conductivity material is theoretically given.The expressions of eddy current effect are given,and the equivalent circuits of wireless charging system with shielding are established.The theoretical influence of shielding on wireless charging system is given in formulas.Through ANSYS Maxwell simulation,the effects of the addition of large-area shielding(such as the chassis)on the DD coils and the circular coils are studied,and the shortcomings of the shielding are indicated.Based on the magnetic core structure design and optimization above,a new shielding structure combined aluminum plate with magnetic core is proposed,and the shielding effectiveness of the new shielding is verified by simulation.And a process of shielding design and optimization is proposed.This paper briefly introduces the building process of the wireless charging system for the electrical inspection robot.The Simulink simulation and experimental design verify the correctness of the frequency splitting theory and the parameter design process of coils.By placing the magnetic cores according to the designed structure,the simulation results and practicality of the new magnetic core structures are verified.Through the robot running experiments of the wireless charging system,the experimental results of the influence of the chassis on the wireless charging system are given,and the correctness of the theory and simulation is verified.