Design method of wide-band high-current air-core inductor EMI filter for high voltage DC power of motor inverter of electric vehicle

Passive filters are often used for electromagnetic interference (EMI) suppression of high voltage (HV) DC power supplies of electric vehicle (EV) motor controllers. The high current of the DC bus saturates the differential mode (DM) magnetic ring, while the leakage inductance of common mode (CM) inductor used as the DM inductance is usually very small, resulting in almost no suppression of DM EMI. A design method of broadband high-current air-core inductor passive filter is proposed. By using the air-core inductor as DM inductor, the problem of easy saturation of the DM inductor core and the small leakage inductance of the CM inductor is solved, and improves the low frequency DM EMI suppression. Through the calculation and selection of the turning frequency point of the multi-stage filter circuit, the effective frequency band can be improved. By analysing the influence of parasitic parameters, the problem of insufficient insertion loss of the filter at high frequency is solved. The experimental verification shows that the proposed air-core inductor filter achieves 50 dB of CM and DM insertion loss in frequency range of 150 kHz–108 MHz, and meets the requirements of system conducted disturbance voltage specified in CISPR25-2016Rd level 3.