Modeling of nanocrystalline common-mode chokes with custom shape by simulation-based extraction of electromagnetic material properties

Knowing the complex relative permeability and permittivity of a ferrite or nanocrystalline core material is crucial to predict the insertion impedance of common-mode chokes. In practice, however, the material properties are often not known across the full desired frequency range. Additionally, factors like core shape, lamination and strip thickness influence the effective permeability and consequently the choke’s impedance behavior. This paper presents a workflow to create core material models that can be used in electromagnetic simulations to estimate the impedance behavior of common-mode chokes. The core’s material characteristics are determined by iteratively fitting model parameters to an impedance measurement using a generic laboratory setup. The resulting core model is then employed to predict the impedance of a common-mode choke in the intended application. • Magentic core’s μ ̲ ( f ) and ɛ ̲ ( f ) are found by fitting simulation to measured impedance. • Presented workflow does not require analytical (starting) solution. • Applicable to cores of arbitrary shapes and unknown inner structure. • Considered frequency range is 100 Hz to 120 MHz. • Above 10 MHz permittivity is relevant. Below, permeability alone is sufficient.