The impedance of the inductor is usually the minimum at a given frequency. The impedance is in series with the line impedance to achieve the desired noise attenuation. It's a pity that most of line impedance is unknown, so designers often use 50 Ω line impedance stabilization network (LISN) filter test. This has become the standard method for testing filter performance, but the results may be as good as the actual real = order filter which can increase attenuation by -6db at each octave frequency. The transition frequency is generally low enough to make the inductance a major part of the impedance, so the inductance can be calculated as follows: Ls=Xs/2 degrees

The first step in the design is usually to choose the size of the magnetic core. If there is a size requirement for the design, as long as the magnetic core can still meet these requirements after being wound, the maximum size of the magnetic core should be selected. If there is no size limit, you can choose the magnetic core size at will. Next, the maximum number of turns required to be wound on the magnetic core is calculated. It is usually a single layer, wound on one end of the magnetic core, isolated from each other. Double-layer and overlapping windings are sometimes used, but these two windings can increase the distributed capacitance of the windings, thus reducing the high-frequency

Since 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 turns can be calculated by dividing the length of each winding by the diameter of the wire and adding the insulation thickness. After calculating the maximum turns, the next step is to select the materials and determine the inductance. Selection of materials takes into account many factors such as operating temperature, frequency range and cost. But first to verify the size of the selected magnetic core, other factors can be considered after sale. So select the right material for permeability and calculate the inductance.