Predicting Radiated Emissions from an Electrical Drive System

A measurement-based SPICE model is proposed to predict radiated emissions from an electrical drive system over a frequency range from 20-300 MHz. The model combines a model for the radiated emissions from the cabling and housings with a model for coupling inside the electrical motor. The electromagnetic properties of the cabling and housings were captured with measured S-parameters. The coupling mechanisms inside the electrical machine were represented using a circuit- element based model. The intent is to provide insight into how coupling mechanisms and placement of structures in the motor affect radiated emissions from the drive system, and to give the designer an opportunity to evaluate the impact of changes to the motor design. The model was able to predict radiated emissions within several decibels of the measurement over the frequency range of interest, to provide insight into strategies for fixing emissions issues, and to provide estimates for the reduction in emissions that could be expected from each fix.