Straightforward Modeling of Frequency Dispersive and Nonlinear Common Mode Chokes for Transient Simulations

The simulation and design process of electromagnetic compatibility (EMC) filters need accurate models for their used components. Common mode chokes, which are essential filter components, exhibit a complex behavior that is usually hard to model for the purpose of transient circuit simulation. This article gives an easy method of modeling such components as long as hysteretic effects can be neglected. The process presented produces an easy to setup and easy to use SPICE model. The incorporated effects are the frequency dependent impedance behavior as well as the nonlinear effect from saturation processes. Both effects are well separated in the model and require only data from the manufacturer, thereby circumventing data fitting methods and measurements on samples with their lead and shipping time efforts. The frequency dependent behavior is modeled via a discrete
RL
-ladder model whereas the nonlinear effects are integrated via treating the saturation as a phase transition. The choke modeling technique was verified for a typical current pulse shape. The comparison between the measurement and the simulation model showed a good match, especially for the maximum amplitude of the current pulse shape, which is essential to determine saturation.