Capacitive coupling interference phenomena between three PCBs placed in a metallic box

Capacitive coupling occurs between conductors, circuits located at different potentials, and among them there are ways of closing the currents produced by the potential difference. The purpose of this paper is to emphasize the capacitive coupling that appears between three PCB´s and to present different methods of reducing capacitive coupling. It was studied the case when three PCBs are placed in a metallic box, each PCB have on his surface three conductors. Paper presents two methods of reducing the parasitic voltages that appear on all inactive conductors. First method is to increase the distance between conductors and the second method is to connect to the ground conductors that are next to perturbation source. The problem is related to the appearance of some disruptive voltages on parallel capacitive coupled conductors. This voltage may appear at the air filters for air purification or electrostatic chargers for electrostatic copy machine.