This reduces the effective permeability from over 1000 to around 137 (see also the calculator of effective permeability).įor smaller gaps the influence of the core is increased and the tolerance could be as wide as ☒5%. to your radios existing coil, wrap a few turns of wire around a ferrite rod. In the example above 150 μm is a relatively large value for the magnetic path of the core, which is 19 mm. How to wind: If you need a small value inductor then just take a pencil or. The tight tolerance of ☓% is possible to attain for proportionally larger gaps. Mixing Iron oxide (Fe2O3) in combination with other metal oxides like (Mn), zinc(Zn) or magnesium(Mg) at a temperature of 1000 C 1300. For the core ER14.5-3-7 this is synonymous with an air gap of 150 μm. Ferrite cores have much lower power loss at high frequencies then silicon steel cores. For example, if your measured value of L in Step 1 is 25 uH, the corresponding AL value will be: AL (100/20)2 x 25uH ( 52) x 25uH 25 x 25uh 625 uH. Step 2: Calculate a coil with a certain inductance or number of turns.

Calculate the AL value using the following formula: AL (100/N)2) x L. Therefore, if the manufacturer provides the A L this simplifies the calculations.Ī typical notation A L=160 nH ☓% means that the core is gapped with such an air gap that A L = 160 nH (per square turn). The AL value is the base relationship between the inductance, with a given ferrite core, and the number of turns. And by comparing the equations it can be seen that the value $x = A_L$ and it is a constant for a given magnetic core of fixed parameters, as long as the effective magnetic permeability is not affected (e.g.

Ferrite core coil inductance calculator