Evaluation of communication error rate induced by common-mode interference of a motor drive system

In a variable-frequency drive (VFD) system, programmable logic controller (PLC) is usually used to control the working states of multiple VFDs. However, the communication performance between PLC and VFD will be affected by common-mode (CM) current in the VFD system, which increases the probability of communication error. In order to enhance the communication performance, it is necessary to evaluate the communication error rate between PLC and VFD. This paper firstly analyzes the interference effect of CM current on communication performance. Then, it investigates the correlation between error rate and two relevant factors, namely, switching frequency and CM current. Based on the method of statistical analysis, a mathematical model for predicting the communication error rate between PLC and VFD is established. The model is verified through comparison between calculations and measurements.