The best brand of common mode inductors in China

FKS CoilS is mainly engaged in the research and development, production and sales of integrated chip inductors, CM, NR, CD, and CDRH. The management team and technical team with more than 10 years of industry experience provide customers with high-quality products and satisfactory services.

Most EMI filters must use common mode inductors. Since the common mode inductor has high impedance over a wide frequency range, it suppresses high-frequency noise generated by high-frequency switching power supplies. The reason why the core of the common mode inductor is ring-shaped has also been introduced before. Here we mainly introduce what factors need to be considered in the design?

The basic parameters required to design a common mode inductor are input current, impedance, and frequency. The input current determines the winding conductor size. A calculation of 400 amps per square centimeter is generally used when calculating the wire size, but other calculations may be used depending on the acceptable temperature rise of the inductor. In almost all cases, single-stranded wire is used because it is not only the cheapest, but its copper loss due to high-frequency skin effect helps to attenuate noise.

The impedance of an inductor usually takes the minimum value at a given frequency. This impedance is in series with the line impedance to achieve the desired noise attenuation. Unfortunately, the line impedance is mostly unknown, so designers often have to test filters with a 50Ω line impedance stabilization network (LISN). This has become a standard way of testing filter performance, but the results may be the same as the actual real first-order filter can increase the attenuation by -6dB per octave beyond the corner frequency. The corner frequency is generally low enough to make the inductive reactance the main part of the impedance, so the inductance can be calculated by the following formula: Ls=Xs/2πf.

After knowing the inductance, the remaining design work is to select the core and material, and calculate the number of turns.

The first step in design is often to select the size of the magnetic core. If there are size requirements for the design, as long as the magnetic core can still meet these requirements after winding, the largest size magnetic core that can be satisfied should be selected. If there are no size constraints, the core size can be chosen arbitrarily.

The next step is to calculate the maximum number of turns required to be wound on the core. Usually a single layer, each wound at one end of the core and isolated from each other. Double-layer and lap-wound windings are also sometimes used, but these two types of winding increase the distributed capacitance of the winding, thereby reducing the high-frequency performance of the inductor.

Because the wire diameter has been determined by the line current, the inner circumference can be calculated according to the value obtained by subtracting the wire radius from the inner radius of the magnetic core. The maximum number of turns can be calculated by dividing the length of the inner circumference of each winding by the value of the wire diameter plus the insulation thickness. After calculating the maximum number of turns, the next step is to select the material and determine the inductance. Material selection is a matter of considering many factors such as operating temperature, frequency range, and cost. But first verify the selected core size, other factors can be considered after sale. So choose a material with a suitable magnetic permeability, and then calculate the inductance.

If you have any demand for inductance, please feel free to contact us, the design of FKS CoilS is guaranteed to give you a big surprise!