Power electronic converters are highly sensitive to electromagnetic interference (EMI), and encapsulation (potting) materials used in high-protection-class systems such as IP66 significantly affect the electromagnetic behavior of the device. While these materials provide environmental protection, they also alter the dielectric environment surrounding the circuitry, increasing parasitic capacitances and leading to resonance-driven conducted emission (CE) peaks. In this study, a CE limit exceedance observed at 2.438 MHz in a power electronics module is analyzed in relation to the relative permittivity (εr) and loss factor (tan δ) of the potting material.
The primary objective is to determine the electromagnetic parameters of the potting material using an inverse characterization methodology, eliminating the need for direct dielectric spectroscopy measurements. For this purpose, an optimization-based frequency-domain model is developed using the measured CE spectrum and known circuit parameters. The material properties εr and tan δ are estimated by minimizing the discrepancy between simulated and measured emission profiles. Sensitivity analysis reveals that higher εr values shift the parasitic LC resonance frequency, whereas low tan δ values fail to provide adequate damping, resulting in increased peak magnitude.
The findings demonstrate that EMC issues arising from potting materials may occur not only during design but also in field applications due to improper material selection. The proposed inverse characterization framework offers a practical engineering tool for extracting dielectric parameters, reducing reliance on laboratory measurements, and accelerating the EMC validation process. This approach enhances the robustness of power electronics packaging and contributes to more reliable, standards-compliant converter design.