Common mode (choke) coil

A filter element that removes noise generated by the potential difference between the power circuit and the ground. It has a structure similar to a transformer with two coils wound on a core with equal turn ratios, and the power supply side wiring and load side wiring are connected to four terminals respectively. Unlike a transformer, the connection method is significantly different, with coils connected in series to each of the two power lines. Since the currents flowing through the two power lines are in opposite directions and the magnetic flux cancels out without mutual influence, only the noise generated between the lines and the ground can be removed. To enhance noise removal performance, a core with high magnetic permeability is often used.