A Laplace Domain Modelling Approach for CM Active EMI Filters

This paper presents a technique to model a Common Mode (CM) active EMI filter designed for suppressing the common mode voltage generated by a three-phase PWM inverter at an induction motor terminals. Detailed mathematical formulas describing the single parts of the system are developed in the Laplace domain. The model is implemented in Matlab Simulink software environment. The software tool is used for the evaluation of the active filter performance in terms of CM voltage attenuation. Laboratory experiments on an induction motor drive confirm the validity of the proposed model.