EMI Behavioral Models of DC-Fed Three-Phase Motor Drive Systems

Behavioral electromagnetic interference (EMI) models based on Thevenin equivalents are proposed for a dc-fed three-phase motor drive system. Both common-mode (CM) and differential-mode (DM) noise models are developed to accurately predict the total EMI noise in accordance with the DO-160 standards for aerospace applications. Beyond the switching frequency of the drive, the CM noise model is found to behave like a two-port linear network and is shown to predict changes in the input-side EMI due to any changes in the load-side parameters or vice versa. Simplified one-port behavioral models for DM noise are then used to predict the total noise at both input and output side of the motor drive. Such models can be very useful in system level EMI analysis and also in understanding how EMI filters and harnesses affect the overall EMI in a motor drive system. The models run in the frequency domain and are validated with experiments up to 30 MHz.