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Inductor with an air-gap calculation yelds dubious results
Posted Mar 6, 2017, 3:33 a.m. EST Low-Frequency Electromagnetics, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.2a 0 Replies
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I have an inductor with an air gap lying around and decided to run some verification tests.
As a first step I calculated its coil without core and got inductance value of L. Both analytic expression and direct measurements of a disassembled coil yielded pretty much the same results within 5% error margin.
Next step I tried adding iron core to the calculation and got inductance value of 10*L. Yet direct measurements showed inductance of only 1.5*L.
I discussed these results with my colleagues and we came to a conclusion that it has something to do with an air gap. Presumably, current used during experiment wasn’t high enough for magnetic flux to permeate iron core, hence such a low inductance value.
But that would also mean that inductance should be gradually increasing with current. I tried to show it in the attached graph. Red line is inductance without a core. Black line is inductance with a core calculated via COMSOL. And blue dashed line is how we think it is supposed to be.
I tried using different material settings but couldn’t achieve desired results.
Any advice? Is there a known solution to calculating systems with air gaps?
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Hello Podryv Ustoev
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