Passing the cable through the ferrite ring to make up a common-mode choke coil.
According to requires, also can increase the coil on the magnetic ring, it has effect in lower frequency blankering, but weak in higher frequency blankering.During actual work, the coil should be adjusted according to the frequency characteristic of interference current.Usually, when the frequency band of the interference signal is wider, two magnetic rings can be sheathed on the cable, and each magnetic ring is surrounded by different coils, which can restrain the high frequency interference and the low frequency interference. From the mechanism of the common-mode choke, the greater the impedance, the more obvious the interference suppression effect.The impedance of the common mode choke comes from the common mode inductance Lcm=jwLcm, and it is not difficult to see from the formula that for a certain frequency noise, the greater the inductance of the ring, the better it would be.But the actual situation is not so, because there is parasitic capacitance on the actual magnetic ring, the existence of it is parallel with inductance. When the high frequency interference signal when the capacitor capacitance is smaller, the magnetic inductor short, so that the common mode choke lose its effect.
Different materials have different permeability and different temperature characteristics.The most important is temperature characteristics, because magnetic rings must undergo constant temperature, high temperature (up to 100 degrees), low temperature, and then work constant in high temperature.However, there is difference in different temperature changing of material, the low permeability will not change temperature too much, but high permeability.The saturation magnetic flux BS varies with different temperatures, In the normal atmospheric temperature, the BS value of 3K material is 200, but when in the 100°C, the value rise up to 300. the same condition, BS value of 2.5K material is 200, but when in the 200°C, the value is just 250.