System-Level Common-Mode EMI Analysis for Drive Applications Using Unterminated Behavioral EMI Models

As wide-bandgap (WBG) semiconductors continue to establish their superior performance in today's power electronics industry, it is imperative that they are equipped with electromagnetic interference (EMI) solutions tailored for their performance characteristics. The increased switching frequency and switching speeds in WBG converters facilitates higher power densities but can adversely affect EMI filtering requirements. This study uses Unterminated Behavioral Models (UBM) to estimate the common-mode (CM) emissions of two individual SiC AC drive systems feeding of the same DC bus, i.e. the effective input CM emission of the system. An extraction procedure for calculating the worst-case emission in the CM range is presented, accounting for the asynchronized and independent operation of both drives. The extraction procedure is developed through experimental UBM development and subsequent frequency-domain, MATLAB script analyses. Experimental results to validate both the UBM and combined input CM noise at various operating points are provided along with details of the physical hardware setup used.