Multiple Resonance Prediction through Lumped-Parameter Modeling of Transformers in High Frequency Applications

The accurate prediction of coupled inductive and capacitive effects in electromagnetic coils is of crucial importance in many industrial applications, due to the increase of operating frequency or to the increase of voltage levels. In this paper, we propose a light-weight coupled electric circuit model that avoids solving a large 3D Maxwell full-wave problem, and is still able to predict not only the first resonance but also the next few resonances as accurately as experimental characterizations would do. The resistive, inductive and capacitive lumped circuit parameters of the magnetic device are identified by means of 2D finite element modelling, and then implemented in an electric circuit that realises the inductive-capacitive coupling. Moreover, the lumped parameter identification can be performed at different levels of representation of the electromagnetic coils, from turn-level to winding-level, in order to resolve additional resonances of the system, still keeping the computational complexity compatible with industrial design requirements. The efficiency of the method is confirmed by means of simulations and measurements performed on a high frequency transformer and on an air inductance.