How to suppress common-mode current by MC equipotentiality in motion controllers

To suppress common-mode current in the motion controller (MC) through equipotential design, it's necessary to reduce the potential difference between different points within the system. Connect all circuit ground reference points to the same star ground point via a low-impedance path, typically the ground center of the power supply filter capacitor. The chassis and internal circuit grounds should be equipotential at high frequencies; this can be achieved by connecting to the chassis via an array of grounding vias at the PCB edge or by using a metal shield. At signal interfaces, employ balanced transmission techniques such as differential signals, which are insensitive to ground potential fluctuations.

For unbalanced interfaces, use common-mode chokes such as the CML series to suppress common-mode current driven by ground potential differences. For long-distance connections, use isolators to break ground loops while maintaining high-frequency equipotentiality through isolation capacitors. After design, measure the voltage difference between each interface ground, especially under interference, to ensure it is lower than the common-mode rejection capability of the receiving circuit. The ultimate goal is to effectively limit common-mode current in the presence of interference, preventing the formation of interference-sensitive loops.