Role of the magnetic core
Oct 30, 2018

Magnetic core: A magnetic core refers to a sintered magnetic metal oxide composed of a mixture of various iron oxides. For example, manganese-zinc ferrite and nickel-zinc ferrite are typical magnetic core materials. Manganese-zinc ferrite has the characteristics of high magnetic permeability and high magnetic flux density, and has low loss characteristics. Nickel-zinc ferrite has characteristics such as extremely high resistivity and low magnetic permeability of less than several hundred. Ferrite cores are used in coils and transformers for various electronic devices.

The magnetic ring that we usually see at one or both ends of the power or signal line of an electronic device is a common mode choke. The common mode choke can form a large impedance to the common mode interference current and has no influence on the differential mode signal (the working signal is a differential mode signal), so the use is simple without considering the signal distortion problem. And the common mode choke does not need to be grounded and can be directly applied to the cable. The number of turns of the magnetic ring The entire cable is passed through a ferrite ring to form a common mode choke. If necessary, the cable can also be wound around the magnetic ring. The more the number of turns, the better the interference suppression effect on the lower frequency, and the weaker the noise suppression on the higher frequency. In actual engineering, the number of turns of the magnetic ring should be adjusted according to the frequency characteristics of the interference current. Generally, when the frequency band of the interference signal is wide, two magnetic rings can be placed on the cable, and each magnetic circle has a different number of turns, so that high frequency interference and low frequency interference can be suppressed at the same time. From the mechanism of the common mode choke action, the greater the impedance, the more obvious the interference suppression effect.

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