Bridging time and frequency domains for fast and accurate common-mode conducted emission modeling in electric vehicle eAxles

Time-domain (TD) numerical models of inverter-fed drive systems can precisely predict conducted emissions (CE), but they are computationally expensive which makes them impractical for design iterations, parametric studies and sensitivity analysis. This paper proposes a reduced-complexity workflow for common-mode (CM) emission analysis. The inverter is first isolated, and its CM voltage is simulated in the TD. The CM voltage is then post-processed to convert the TD waveform to the frequency domain (FD) spectrum with standard detector algorithms, ensuring meaningful results. The remaining system components are represented by a CM equivalent circuit which is excited with the extracted FD CM voltage. The method is validated in two experimental bench setups: an inverter directly connected to an electric motor (eMotor), which represents a real electric axle (eAxle) system with a high degree of complexity and integration, and an inverter connected to AC cables with an equivalent load. Results demonstrate remarkable agreement between the proposed workflow and the full TD reference models across 9 kHz–10 MHz, under different operating scenarios by changing switching frequency, modulation index, DC operating voltage, and various detector algorithms. The approach drastically reduces simulation time from several hours to a couple of minutes, while maintaining the entire TD result. This makes it an efficient tool suitable for early-stage designs and filter tuning, etc.