Introduction to the working principle of common mode inductors1

The working principle of common mode inductor:

The common mode inductor is a common mode interference suppression device with a ferrite core. It consists of two coils of the same size and the same number of turns wound symmetrically on the same ferrite toroidal core to form a four-terminal The device has a suppressing effect on the common-mode signal with a large inductance, but has little effect on the differential-mode signal with a small leakage inductance. The principle is that when the common mode current flows through the magnetic flux in the magnetic ring, the magnetic flux in the magnetic ring is superimposed on each other, which has a considerable inductance, which inhibits the common mode current. When the differential mode current flows through the two coils, the magnetic flux in the magnetic ring The channels cancel each other out, and there is almost no inductance, so the differential mode current can pass through without attenuation. Therefore, the common mode inductance can effectively suppress the common mode interference signal in the balanced line, but has no effect on the differential mode signal normally transmitted by the line.​​

Common mode inductance is a high permeability magnetic core with two windings. The currents of the two windings flow in and flow out in the same direction, and the magnetic fields generated by the load current cancel each other in the magnetic core. When the common mode noise flows in, the magnetic field is generated in the magnetic core due to the different directions, and the noise is suppressed due to the high magnetic permeability of the magnetic core.