Suppressing Common Mode Current By Using Electromagnetic Losses

With the power electronic technology developing and high-power integrated devices are widely used, causing the electromagnetic environment problem becoming more and more serious, system to control electromagnetic interference has received extensive attention of the whole society.Common-mode current are widespread in the electric car, printed circuit board, ship power system and other electronic circuit system, is one of the important reasons to produce electromagnetic interference.Typically, high-power power converters of electric vehicles in the course of their work will produce broadband electromagnetic noise and electromagnetic interference, which are mainly in the form of common-mode currents propagate along the cable and chassis, affecting the normal operation of the vehicle electrical equipment and control systems, resulting in serious electromagnetic compatibility problems,it is not conducive to the reliable operation of the electric vehicle and its industrialization process.According to transmission line theory, the common-mode current and electromagnetic wave are existing in the form of waves. Analogy in the absorbing material in microwave absorbing applications, we put forward the new way of using the electromagnetic loss inhibit common-mode current. We design one of common mode current suppressor by studying the basic characteristics and the main factors influencing of size, spatial distribution and frequency range of the common mode current in electric vehicles,on this basis,focusing on the drive motor and converter output terminal connected ten meters long cable of electric passenger cars. Simulation results show that the choice of suitable materials electromagnetic losses can significantly suppress common mode currents over a wide frequency range and the inhibitory effect has nothing to series position.The research provide necessary theoretical basis and feasible technical solutions for curbing broadband electromagnetic noise,electromagnetic interference and the optimal placement of cable in vehicle and also reveals the possibility of using electromagnetic functional materials to adjust the circuit performance.