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

Abstract

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.

Optimal Design of Single-Layer and Multi-Layer Air-Core Inductors Considering Uncertainty Factors

“…The computed stray capacitance C tot is 1.2 pF, and the computed SRF is 19.9 MHz. The inductance and stray capacitance of the prototype are obtained by fitting the input impedance of the prototype measured by an impedance analyzer through an RLC circuit model [1]. Table 3 compares expected parameters and the measured data for the inductor, revealing an excellent agreement.…”

“…A IR-CORE inductors are widely used in EMI filters [1], power electronic converters [2], and line impedance stabilization networks (LISNs) [3] with the advantage of avoiding hysteresis and eddy-current losses and holding large currents without saturation. However, because of their inherent capacitance (stray capacitance), the inductive behavior of air-core inductors is constrained up to the first selfresonant frequency (SRF), limiting the potential performance of designed applications at high frequency.…”