A Universal DM/CM Physical Model for Power Transformer EMI Analysis within both Conducted and Radiated Frequency Ranges

Transformer modeling is important for EMI prediction and suppression. Existing modeling techniques only focus on either differential mode (DM) model or common mode (CM) model. However, these models are inaccurate for high-frequency range above 10MHz. This paper proves that the inaccuracy is mainly due to the current coupling between DM path and CM path. This paper proposes a simple physical model. It also quantifies how the DM components can influence the CM impedance and how the CM parasitic components can influence the DM impedance. The effects of different ground connections can also be analyzed with the model. Experimental results verify that the proposed model is accurate within both conducted and radiated frequency ranges from 150 kHz to 100 MHz.