Modeling-based examination of conducted EMI emissions from hard- and soft-switching PWM inverters

For the study of electromagnetic interference (EMI) mechanisms in pulsewidth-modulated inverters, this paper presents an analysis approach based on empirical models of the inverter components and their associated various parasitics. The power switching devices were modeled with a physics-based device modeling technique. Using time-domain reflectometry, the authors characterized the major parasitics in the device modules, passive components, cables, leads and interconnects. Simulations of a full-bridge insulated gate bipolar transistor inverter were then carried out in the time domain under hard-switching and zero-voltage switching conditions. The simulated EMI spectra were compared with the experimental counterparts with the separation of common-mode and differential-mode EMI. The comparisons verified the validity of the proposed modeling approach over most of the EMI frequency range. Also discussed in the paper are the soft-switching effects on the inverter's EMI.