Modeling and evaluation of common-mode interference coupling effects on sensitive cable in motor drive system

Electromagnetic interference (EMI) couplings between motor drive and adjacent communication network induce a considerable common-mode (CM) current in sensitive communication cable, which increases the probability of communication error and threatens the reliability of the overall system. In order to improve the communication performance, it is necessary to study the coupling mechanism between the motor drive and the communication network, and to evaluate the effect of the EMI coupling. In this paper, a commercial motor drive system with RS485 communication circuit is used for analysis. The conducted and near-field coupling paths are analyzed and modeled. And a model for estimating the CM current coupled to GND cable is proposed. Besides, communication error rate is employed to evaluate the effect of coupling, and the correlation between error rate and CM current in communication GND cable is established by statistical analysis. And the estimation models of CM current and error rate are validated by measurements.