EMI terminal modelling of dc-fed motor drives

A three-terminal noise-model has been shown earlier to predict the common-mode noise currents at the input and output side of a dc-fed motor-drive system. Accuracy of this model was found to be good up to 30 MHz. The DO-160 standards for aerospace applications however are based on total noise and hence simulations based on common-mode model alone are inadequate for EMC compliance. This paper proposes simple terminal models to predict the differential mode noise currents in a motor-drive system. In the end, predictions from the common and differential mode models will be combined to estimate the total noise at the input and output side of the motor-drive system. The proposed method is validated with experiments.