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Registered Member #39190
Joined: Sat Oct 26 2013, 09:15AM
Location: Boise National Forest
Posts: 65
It's pretty clear that a lot of people here aren't looking to save money on their HV pursuits. Then there is the rest of us...
Surprised at how excellent Chinese HV ceramic caps were, I thought I'd dabble into undocumented Chinese ferrites. All throughout the 'net (ebay, alibaba, aliexpress, blinq, walmart.com, etc) are advertised 'green' ferrite toroids. Now if we were talking iron powder toroids and we were talking green and blue, it would be a different story. That clearly signals #52 material. But just a 'green' ferrite tells me next to nothing. (If it tells someone else something more, please enlighten me.)
I'll attach a photo illustrating two different types of ferrite toroids I've purchased and used. The smaller emerald green toroids seems to have a rather high mu, sort of like a type J or W material. All I know for sure is that they make great GDTs in the 10kHz - 100kHz range. The larger and lighter green toroids seem to have a somewhat lower mu. And all I know about them is that when stacked together and wrapped with a heavy-gauge primary they make a great transformer for a series-fed induction heater.
BTW, it's not that vendors like Amidon and Surplus Sales don't have great prices on magnetics. It's that a ~$20 minimum shipping charge destroys the economy of their prices.
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
Location:
Posts: 80
The smaller ones look like many I have salvaged from ferrite cm chokes in atx supplies, similar to the uncoated ones that are usually in a plastic housing. They do work well for lower freq gdt's, and also work pretty well for CT's Large ones, no idea...
Registered Member #39190
Joined: Sat Oct 26 2013, 09:15AM
Location: Boise National Forest
Posts: 65
"Are the yellow and white ones not powder metal too ?"
Yes. The yellow and white toroids on at ATX supply are #26 powdered iron.
"The smaller ones look...similar to the uncoated ones...in atx supplies...that are usually in a plastic housing."
Could very well be the same material. At least one internet source indicates the toroids you mention are ferrite and not iron powder. For certain the emerald green toroids in my pic are not iron powder. Indeed the mu was so high that I wondered fleetingly if they were amorphous steel. But they perform too well at high frequencies to be that.
Since I have a few ATX supplies in various states of salvage, I'll look for such a toroid and then compare it against the emerald green cores.
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
Location:
Posts: 80
woodchuck wrote ...
"Are the yellow and white ones not powder metal too ?"
Yes. The yellow and white toroids on at ATX supply are #26 powdered iron.
"The smaller ones look...similar to the uncoated ones...in atx supplies...that are usually in a plastic housing."
Could very well be the same material. At least one internet source indicates the toroids you mention are ferrite and not iron powder. For certain the emerald green toroids in my pic are not iron powder. Indeed the mu was so high that I wondered fleetingly if they were amorphous steel. But they perform too well at high frequencies to be that.
Since I have a few ATX supplies in various states of salvage, I'll look for such a toroid and then compare it against the emerald green cores.
There are other small plastic toroids in atx as well, they feel hollow, but have some sort of brittle silver ribbon. I couldn't find any info on those... The ones I referred to would be part of the ac filter most likely near the varistor and mkp capacitors, usuallly 2 of them.
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Green ferrite toroids
