Difference Between Inductor Magnetic Core And Iron Core

Inductor iron core is a type of reactor that uses iron core, which is small in size and uses less copper.

Due to the nonlinearity of ferromagnetic materials, their inductance remains basically unchanged when the passing current is small, but decreases when the passing current is large, and the current and voltage are not linearly related. To reduce this nonlinearity, an air gap is often opened in the magnetic circuit of the iron core.

The magnetic core of an inductor, which 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 against the common mode interference current without affecting the differential mode signal (the working signal is a differential mode signal), so it is simple to use without considering signal distortion issues. And the common mode choke does not need to be grounded and can be directly added to the cable. The number of turns of the magnetic ring is chosen by passing the cable through a ferrite magnetic ring to form a common mode choke. As needed, the cable can also be wound several turns on top of the magnetic ring. The more turns, the better the suppression effect on interference with lower frequencies, while the weaker the suppression effect on noise with higher frequencies. In practical engineering, the number of turns of the magnetic ring should be adjusted based on the frequency characteristics of the interference current. Usually, when the frequency band of the interference signal is wide, two magnetic rings can be placed on the cable, each with a different number of turns, which can simultaneously suppress high-frequency interference and low-frequency interference.

From the mechanism of the action of the common mode choke, the larger its impedance, the more obvious its interference suppression effect. The impedance of the common mode choke coil comes from the common mode electric Lcm=jwLcm. It is not difficult to see from the formula that for a certain frequency of noise, the larger the inductance of the magnetic ring, the better. But this is not the case in reality, as there are parasitic capacitors on the actual magnetic ring, which exist in parallel with the inductance. When encountering high-frequency interference signals, the capacitive reactance of the capacitor is small, which shortens the inductance of the magnetic ring and makes the common mode choke ineffective. According to the frequency characteristics of the interference signal, nickel zinc ferrite or manganese zinc ferrite can be selected, with the former having better high-frequency characteristics than the latter. The magnetic permeability of manganese zinc ferrite ranges from thousands to tens of thousands, while nickel zinc ferrite ranges from hundreds to thousands. The higher the magnetic permeability of ferrite, the greater its impedance at low frequencies and the smaller its impedance at high frequencies. Therefore, when suppressing high-frequency interference, nickel zinc ferrite should be selected; On the contrary, manganese zinc ferrite is used. Alternatively, both manganese zinc and nickel zinc ferrite can be sheathed on the same bundle of cables, which can suppress interference in a wider frequency band. The larger the difference between the inner and outer diameters of the magnetic ring, the higher the longitudinal height, and the greater its impedance. However, the inner diameter of the magnetic ring must be tightly wrapped around the cable to avoid magnetic leakage. The installation position of the magnetic ring should be as close as possible to the interference source, that is, it should be close to the inlet and outlet of the cable.