Comparison of Differential-Mode and Mixed-Mode Conducted Emission for Household Appliances in Power-Line Communication System

Electromagnetic interference (EMI) from the low-voltage power-line network has been a major concern for the power-line communications (PLC) technology. The conventional EMI measurement is based on the mixed mode, including common mode, and differential mode (DM). However, the dominant transmission mode of PLC is DM. Therefore, for electromagnetic compatibility designing purposes, knowledge of the DM noise of the household appliances in the frequency range of 150 kHz to 30 MHz is essential to provide insight of conducted disturbance on the low-voltage power-line network. In this paper, a simple and useful method of DM conducted emission (DMCE) measurement using a PLC coupler is proposed and it offers a suitable interface and a convenient way for the household appliance to obtain the DMCE with the existing equipment. The obtained results compare the levels of DMCE and mixed-mode conducted emission (MMCE) from different kind of household appliance. It shows that even when MMCE meets the current limits in standard CISPR 14, DMCE may still exceed these limits. In order to suppress EMI on the PLC network, the limits and measurement methods of DMCE for the household appliance should be taken into account in the future.