143 – Inductance Analysis of an Air Core Coil

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Application Note / Model Data


Electric components such as choke coils and chip inductors are used for purposes such as reducing electromagnetic noise by taking advantage of their own inductance. Air core coils have smaller inductance than those with cores, but because they do not use cores with nonlinear magnetization properties, they maintain linearity in their inductance and can therefore be used in high-frequency filters and oscillators.
In a coil with a core, most of the magnetic flux flows in the core, but because the magnetic circuit in an air core coil is not as clearly structured as in a core, the inductance is easily influenced by the coil’s dimensions and geometry. Because of this, it is necessary to accurately understand the inductance by analyzing the flow of magnetic flux in the air region.
This analysis shows how to obtain an air core coil’s inductance through analysis and compare it with theoretical values.

Magnetic Flux Density Distribution/ Inductance

The magnetic flux density distribution in the coil and the air region around it is shown in fig. 1 and the coil’s inductance is shown in table 1. The inductance from the analysis results is compared to theoretical values.
Fig. 1 shows that the density of the coil’s flux linkage is higher in the center of the coil. The difference between the inductance obtained from the flux linkage and theoretical values is 0.28%. This confirms that essentially accurate inductance can be obtained using analysis.

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