Introduction to the working principle of common mode inductors -

The working principle of the common mode inductor:

The common mode inductor is a common mode interference suppression device with ferrite as the core. It consists of two coils with the same size and the same number of turns symmetrically wound on the same ferrite ring core to form a four-terminal Devices that exhibit large inductance for common-mode signals have a suppressive effect, but exhibit small leakage inductance for differential-mode signals that have little effect. The principle is that the magnetic flux in the magnetic ring is superimposed on each other when the common mode current flows, so that it has a considerable inductance, which inhibits the common mode current, and when the two coils flow through the differential mode current, the magnetic flux in the magnetic ring Through canceling each other, there is almost no inductance, so the differential mode current can pass without attenuation. Therefore, common-mode inductors can effectively suppress common-mode interference signals in a balanced line, but have no effect on differential-mode signals normally transmitted by the line. the


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