The essence of common mode inductors

The essence of common mode inductors   Common-mode inductance, also called common-mode choke, is a coil with the same number of turns and opposite winding directions on a closed magnetic ring. An ideal common-mode choke has a suppressive effect on the common-mode interference between L (or N) and E, but has no inductive suppressive effect on the differential-mode interference between L and N. However, the incomplete symmetry of the actual coil winding will lead to the generation of differential-mode leakage inductance. When the signal current or power current flows through the two windings in opposite directions, the magnetic flux generated cancels each other out, and the choke presents low impedance. When the common-mode noise current (including the disturbance current caused by the ground loop, also called the longitudinal current) flows through the two windings in the same direction, the magnetic flux generated is added in the same direction, and the choke presents high impe…