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What is an ETD59 core set (N87 ferrite) with AL = 250?

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Jun 13, 2021
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The following claims to be an ETD59 core with AL=250.

....Does this mean that one of these halves, coupled with a totally ungapped half, gives an AL of 250?

(or do you need two of these gapped ones together?)

The accompanying datasheet doesnt say

....With "normal gapped" cores, the other half is not gapped...but these are brand new "distributed gap" cores, and nothing is said about how you get the AL=250

The following video...
...makes it appear that two "distributed gap" cores are needed to be mated together...if so, then that is a deviation to the older non distributed gap cores...where the "other half" was always ungapped.
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I had bought around 20K units of Al200 gapped PQ2625 cores form TDK twice and they delivered one gapped and one un-gapped core pair. I asked the distributor about gap configuration but he said that for some AL values it is both gap and for some it is single gap and that we can not be sure unless we enquire from the sales team. But since the cores came in pair it wasn't a problem.
However on the link you have mentioned ships in single unit so apparently there's no sure-shot way to determine the gap configuration.
But since the datasheet mentions delivery mode as single unit and no where mentions any other part number, I guess the gap dimensions mentioned are for a pair and not one gapped and one un-gapped.
The distributed gap design doesn't make much sense if it's paired with an ungapped core, isn't it? If you don't believe, you can also calculate required gap width for the Al values.
Thanks, yes i think the confusion arises because they have "stolen" the term "distributed gap".......AYK, what they have done is not a "distributed gap"....that is something looks like an ungapped core but is made up of a mix which is literally incorporating the gap all evenly amongst it in a single homogenous mixture....but what TDK have done, is more like a "spread-gapped core"...which kind of makes you wonder if the AL values they quote do indeed belong to the "ungapped" and "distributed gapped" halves....they could do after all, and it would still be a "more distributed gap" core than the old variety.

AL 250 - indicates a small gap - usually just on one of the core halves - the reduces the reluctance - such that more ampere turns can be applied to the core for the same B.

Often a gap is employed in flyback converters, or to lower the Lmag of a transformer for LLC, for example.

core come in several standard gaps sizes with AL values stated - and of course you can just separate standard ungapped cores a bit for the same effect.
Beyond sophistic hair-splitting, if a manufacturer of magnetic components advertizes "distributed gap" ferrite core, I expect something similar to the TDK core.
the distributed gap cores mentioned in the links above are a response to requests for such constructions in an effort to reduce " gap loss " where the windings are close to larger gaps ( usually only in the centre ).
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