How can industrial servo systems reduce high-frequency grounding impedance?

Reducing the high-frequency impedance of the servo system grounding is crucial for suppressing common-mode radiation and improving immunity. Etymotic's impedance reduction measures include: First, using wide and short tinned copper busbars for rack grounding (recommended width >25mm, length <0.5m), with multi-point welding between the busbars and the rack frame, resulting in a contact resistance <1mΩ. Second, using an array distribution (e.g., 2mm spacing) for grounding vias on the PCB, and employing electroplating to fill the vias, reducing inductance.

For IGBT modules, conductive silicone grease is used between the mounting base and the heatsink, and the modules are connected to the chassis via multiple metal screws. Parallel connection of high-frequency ceramic capacitors (e.g., 100nF/630V C0G) along the grounding path can "shorten" the high-frequency current path. Using an impedance analyzer, the goal is to reduce the grounding system impedance to below 100mΩ at 30MHz. Experimental results demonstrate that low-impedance grounding can reduce the radiated emission peak of the device in the 80-200MHz range by 6-10dB and significantly improve EFT/B immunity levels.