Yujie Lan

Common mode chokes (CMCs) are key components in electromagnetic interference (EMI) filters, and accurate modeling of these components is critical for filter design and EMI noise simulation. This paper proposes a behavioral model and parameter extraction technique for characterizing three-phase four-wire common mode chokes (4W-CMCs). The proposed model considers the inductance nonlinearity caused by the nonlinear permeability of manganese-zinc ferrite and nanocrystalline magnetic materials, as well as the asymmetry and local symmetry in the winding distribution of 4W-CMCs. The parameters for the common mode (CM) and differential mode (DM) models are extracted using a parameter extraction program and a simple equation-based method, respectively. For the DM model parameter extraction, this paper proposes a measurement method that utilizes the local symmetry of 4W-CMCs. The equivalent circuit of this measurement method decouples the inter-winding capacitance (CW) from the differential mode inductance parallel capacitance (CD) by transforming two-port network parameters, greatly simplifying the parameter extraction process. The accuracy of the model and the effectiveness of the method are validated through experiments using several 4W-CMCs with manganese-zinc ferrite and nanocrystalline magnetic cores.

The complex permeability of magnetic materials at radio frequencies significantly impacts the electromagnetic compatibility characteristics of magnetic components. The precision of its measurement is crucial for the design, selection, and study of electromagnetic compatibility properties of magnetic components. This paper discusses the key material parameters affecting the radio frequency characteristics of magnetic materials and provides a detailed analysis of how these parameters influence the complex permeability of magnetic materials. It reveals why traditional methods for measuring the complex permeability of magnetic materials are not applicable at high frequencies. The paper identifies the parasitic inductance and capacitance in the measurement winding as the primary factors affecting measurement accuracy. Consequently, it proposes a new method for testing the complex permeability of magnetic materials in the radio frequency range, considering the effects of parasitic parameters in the measurement winding. This method effectively combines small-signal measurements with finite element simulation to calibrate parasitic parameters, significantly extending the frequency range of the measurement results. Experimental findings demonstrate that the proposed method accurately extracts the characteristic parameters of magnetic materials in the frequency range of 30 MHz to 1 GHz.

With high power density and high-frequency power electronics technologies, parasitic capacitances of inductors and transformers have been widely discussed, in which parasitic capacitance may lead to electromagnetic interference (EMI) and efficiency performance degradation. Therefore, it is significant to analyze and model the parasitic capacitance of the inductors and transformers. This paper proposes a new parasitic capacitance calculated model of multilayer windings inductors and transformers. Based on the electromagnetic field theory, it can fully consider the edge effect of multilayer inductor windings, including the edge effect between adjacent and non-adjacent layers. Finally, the accuracy of the model is validated by simulation and experiment. Compared with the traditional parasitic capacitance calculated method, the proposed model can calculate the parasitic capacitance more accurately, and the maximum error between calculations and simulations is less than 8%.