81 – AL-value Analysis of a Choke Coil

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Application Note / Model Data


A choke coil is an electric component that is intended to filter high-frequency current. The AL-value is a vital parameter in a choke coil design that determines the cutoff frequency of a high-frequency current.
The AL-value varies greatly depending on gap width, so it is effective for the advance study of a design to accurately obtain the AL-value dependency on the gap width (air gap versus AL characteristics) for the geometry of a choke coil by using a finite element analysis (FEA).
This Application Note explains a case example that obtains the air gap versus AL characteristics of a choke coil.

Air Gap-AL Characteristics

The air gap versus AL curve of the choke coil is shown in fig. 1.
Fig. 1 demonstrates the relationship between the gap width and the AL-value. This makes it possible to obtain the AL-value from the gap width and estimate the number of turns to achieve the specified inductance.

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