CM and DM conducted EMI modelling of PMSM VSD system with non‐ideal LISN

Abstract

In this study, a non-ideal single-phase 50 Ω, 50/250 μH + 5 Ω V-network line impedance stabiliser network (LISN) is modelled, to show how the impedance characteristic of the LISN affects the common-mode (CM) and differential-mode (DM) conducted electromagnetic interference (EMI) modelling and measurements. The equivalent CM and DM single-phase models of a permanent magnet synchronous motor (PMSM) variable speed drive (VSD) system are developed based on CM and DM impedance characteristics of different parts of the system. Using the proposed single-phase CM and DM circuits, the authors introduce the LISN correction factor, which shows the relation between the EMI measured in different frequency ranges and the LISN impedance characteristic. The LISN correction factor is calculated for three different cases. It is shown how the EMI measurement can be modified by the LISN correction factor to have more accurate results. MATLAB Simulink is used for the time-domain analysis of the system. However, the proposed method can be used in both frequency-domain and time-domain analyses. Results given by the proposed method is verified with experimental EMI measurements. The outcome of this study can be used for a more accurate conducted EMI prediction, measurement, and a better EMI filter design.