构成平面EMI滤波器元件电磁参数的提取

平面型电磁干扰(electromagnetic interference,EMI)滤波器因其易于进行磁集成、寄生参数小、抗电磁干扰强等优点在航空领域具有很好的应用前景。论文提出一种以"圆环型"结构为基础的EMI共模、差模模块,其中,前者通过将"电感和电容"(LC单元)集成于一体构成,后者利用前者泄漏的磁场而形成的漏感和一个独立的差模电容器构成。提取这些模块单位长度的电磁参数是分析各模块甚至整个滤波器特性的基础。论文建立LC单元的轴对称静电场模型,提取各线匝之间的部分电容;建立LC单元线匝系统的时谐磁场模型,在计及线匝导体集肤效应、邻近效应、磁芯损耗的基础上,提取了各线匝电感、电阻;建立LC单元形成漏感的时谐场模型,并提取该漏感,该漏感即为差模电感;差模电容可以直接采用平行板的近似表达式求得。结合适当的边界条件,利用所建立模块的分布参数模型对其阻抗的频率特性进行了测试,验证了提取参数方法的正确性和数值的准确性。

Extraction of Magnetic Parameters for Planar EMI Filter Elements

The planar electromagnetic interference(EMI) filters have a good application prospect in aviation for the advantages of easy magnetic integration,small parasitic parameters and strong anti-EMI ability.Based on the annular structure,the common-mode(CM) and difference-mode(DM) modules were proposed.The former one was formed by the ’capacitance and inductance’(LC unit),and the later one was formed by an independent DM capacitor and the leakage inductance leaking from the LC units.The extraction of the unit-length electromagnetic parameters was the foundation for analyzing each module,even the characteristics of the whole EMI filter.The axisymmetric electrostatic field model of LC unit was established to extract the turn-to-turn partition capacitances.Considering the skin effect,proximity effect and core loss,the model of harmonic magnetic field of the LC unit system was also established to extract the inductances and resistances.The leakage inductance could serve as the DM inductance.So,the model of harmonic magnetic field with leakage layer between LC units was presented to extract this parameter.The DM capacitance could be calculated directly using the approximate expression of the parallel-plate.Under the appreciate boundary conditions,the frequency properties of impedances were measured with the established distributed-parameter model.The results verify the validity of the proposed extraction method and the accuracy of the extracted parameters.