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The iron powder core material, as you may know, has a continuous air gap in its structure. However, do you think it is possible to add a continuous air gap (for example 1mm) to the iron powder cores? I know that we can add this kind of air-gaps to ferrite material, but is it going to create a problem if we add a gap in iron powder cores?

thank you

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  • \$\begingroup\$ Use a thin abrasive cutting wheel in a Dremel. \$\endgroup\$
    – user16324
    Sep 4, 2018 at 20:37

2 Answers 2

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You can create an air gap in laminates if you do it carefully so providing you can effectively trim the iron powder core without damaging it, yes you can.

but is it going to create a problem if we add a gap in iron powder cores?

As with any non-homogenious gap in a ferrite or iron core, the leakage flux can be a problem to the wire turns located close by because, the flux density local to the air gap can cause a significant heating of the copper due to localized eddy current induction. This is because the flux is not "contained" within the main body of the core however, it doesn't normally cause an issue unless the power is significantly high.

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However, do you think it is possible to add a continuous air gap (for example 1mm) to the iron powder cores?

If your manufacturer can manufacture it with a gap, or you can build one yourself then yes.

I know that we can add this kind of air-gaps to ferrite material, but is it going to create a problem if we add a gap in iron powder cores?

What you really need to do is design your core for how much Magneto Motive Force (MMF) you desire to go around your core. Adding an air gap is like adding a resistor in the circuit, and limits how much MMF can flow around the core. First find the max MMF you want around the core. Find the reluctance of the core, then design your air gap to increase the reluctance of the core to your max MMF value.

There is a good guide on how to do this here: http://info.ee.surrey.ac.uk/Workshop/advice/coils/gap/index.html

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    \$\begingroup\$ MMF is ampere turns and so adding an air gap has really nothing to do with changing the value of MMF if the current is controlled. In AC circuits, MMF (aka current) is determined by coil inductance and so at higher frequencies the current is less and therefore the MMF is less but, with an air gap, the inductance drops significantly so this can mean the amps rises significantly and therefore your assertion that adding an air gap limits MMF is wrong. Adding an air gap reduces the flux density for a given MMF, or stricly speaking it reduces B for a given H-field. \$\endgroup\$
    – Andy aka
    Sep 4, 2018 at 19:00

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