The choice of the circular

We at ordinary times in the electronic equipment of the power cord or the circular end or ends see line is the common mode choke. Common mode choke coil to form a larger impedance common-mode interference current, but has no effect on the differential mode signal ( Working signal for the differential mode signal) , so simple to use without considering signal distortion. Do not need grounding and common-mode choke coil, can be directly added to the cable. The entire cable through a ferrite beads will constitute a common mode choke coil, according to the needs, can also be cable on magnetic ring around a few turns. The more number of turns, the low frequency interference suppression effect, the better, and weak of high frequency noise suppression effect. In actual engineering, according to the frequency characteristics of interference current to adjust the number of turns of the circular. Usually when the interfering signal frequency band is wide, can be in position two copper cable and each magnetic around a different number of turns, it can suppress the high frequency interference and low frequency interference at the same time. Look from the mechanism of the common mode choke effect, the impedance, the greater the interference suppression effect of the more obvious. And the common mode choke coil impedance from common-mode inductor LCM = JWLCM, it is not hard to see from the formula, to a certain frequency noise, the greater the inductance of the circular, the better. But it's actually not the case, because the actual magnetic ring and parasitic capacitance, it is way of being with inductance in parallel. When faced with high frequency interference signals, the capacitance of capacitive reactance is small, the circular and the inductance of short circuit, so that the common mode choke. According to the frequency characteristics of the jamming signal can choose nickel zinc ferrite or manganese zinc ferrite, frequency characteristic of the former is superior to the latter. Manganese zinc ferrite magnetic permeability in thousands of - - - - - - - - - - - - - Tens of thousands, and nickel zinc ferrite is a few hundred - - - - - - - - - - - - - Thousands of. Ferrite magnetic permeability is higher, the low frequency impedance, the greater the high frequency impedance of the smaller. Therefore, in the high frequency interference suppression, appropriate chooses nickel zinc ferrite; The opposite with manganese zinc ferrite. Or on the same cable at the same time set of manganese zinc ferrite, zinc and nickel that can restrain the interference of spectrum is wide. Circular and the diameter of the difference, the greater the vertical height, the greater the its impedance was greater, but the circular bore certain important cable, prevent leakage. The installation position of the circular should try to be close to the interference sources, which should be close to the import and export of the cable.