Debunking The Gapped Inductor Myth
by Gregory Mirsky, Vitesco Technologies, A Spinoff Of Continental Automotive Systems, Deer Park, Ill., How2Power Today, Feb 14 2020
Focus:
According to the author, many engineers mistakenly believe that power inductors with an air
gap in the magnetic core store energy in the gap only. As this article explains, the energy
is stored in the whole gapped magnetic, with the energies stored in the gap and the rest of
the core in reverse proportion to the permeabilities of air and the magnetic material. As
part of this discussion, a new approach to designing gapped-core inductors is presented.
This procedure begins by designing a distributed-gap-core inductor. Then designers
calculate the real physical air gap that would be required for the equivalent air-gaped
core. This method simplifies the calculations, while also allowing for more-accurate sizing
of the gap. At the same time, this procedure defines the parameters for a distributed-gap
core, which may be a real option for the design. The equations derived here are used to
obtain an expression for the ratio of power stored in the gap to power stored in the rest
of the core, which is the same as the ratio of energy stored in each part.
What you’ll learn:
- How to design gapped-core inductors for power converters accurately and simply
- How to understand how gapped-core inductors store energy in the whole core not just the gap
- How to understand why an air gap does not increase the saturation flux density of a power inductor
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