Measurements and Simulation of Common Mode Conducted Noise Emissions in Adjustable-Speed AC Drive Systems

In order to efficiently reduce EMI emissions, especially common mode (CM) conducted noise emissions that are the most disturbing in any adjustable-speed drive systems, behaviour understanding and propagation path knowing of parasitic currents in the system are indispensable. In this paper, a simple CM disturbances modelling is proposed to estimate or calculate the CM noise currents. The modelling principle is based on specific experimental characterizations and on the modelling of the complete CM circuit considered as a chain of quadripolar matrices. Each part of the system is represented by a two-port network associated in cascade by using transfer matrix [T]. The comparison between calculations and experiments in an adjustable-speed drive system confirms effectively the validity of the proposed approach. Parametric studies carried out herein using this valid model will show in which way CM currents could be reduced or eliminated in a considered existing system.