I have around 100 120v:11.5v 80VA power transformers that I am trying to find a use for. They are basically factory seconds with various connector issues, etc. I also have a more or less unlimited supply of 26awg magnet wire from shaded pole fan motors of the same situation. I am thinking about cutting the "El" cores of the transformers open, 3d-printing bobbins and making "EE" core filter reactor chokes with an air gap between the "E" sections to prevent saturation because of the DC. Maybe lay a piece of fish paper between them for better insulation/separation. 26 awg isn't very thick, but I could wind several conductors in parallel for better current capacity. Does this idea have any merit at all? Is there a better way of going about it? All of this stuff is going straight into the trash if I don't snatch it up first, and I hate seeing it go to waste.
Edit: I also have a cache of microwave oven transformers as well, which I have done several things with. I've considered the same "EE core with air gap" format using them instead. They'd be huge, but I imagine the inductance would be huge as well. I'd of course cut the original windings out.
Edit: I also have a cache of microwave oven transformers as well, which I have done several things with. I've considered the same "EE core with air gap" format using them instead. They'd be huge, but I imagine the inductance would be huge as well. I'd of course cut the original windings out.
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If you need only a small inductance, there are ways to fine tune the transformer leakage (externally) to get what you want, without having to cut anything. However, you would have to short circuit the other winding to "remove" the transformer.
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Okay, cool beans. Thank you for researching that. Cutting the iron isn't much of an issue. I would just like a "free" way of getting decently large-value chokes for power supply filtering. I'm starting to look into regulation now too, and some of those designs still call for chokes before the regulator portion. I have to admit too that I kinda like the idea of making the components myself instead of just buying something especially if I saved parts from the bin in the process.
FORGET cutting silicon steel laminations, very hard and brittle alloy.
No regular saw, not even a dedicated metal bandsaw will cut it decently, a diamond edge abrasive wheel neither , both will leave too rough edges and surfaces, lots of sharp burrs, etc.
Original EI were cleanly *punched*, not cut, using very hard steel sharp dies, in large mechanical presses.
I know, I have custom EI and strips made out of it.
Your best bet is to**disassemble** EI lamination packs, think leaving them overnight in an acetone tank to soften varnish *or* Toast them with a propane torch so it becomes brittle and a couple hammer hits loosens them.
You *might* be ableto recover wire using the second method (I have) if you heat iron only and do not burn wire.
Forget 3D printing 100 bobbins, use a regular size and buy them or maybe you can recover original ones.
Or wind over paper-cardboard DIY cores.
Try to recover original wire first.
Unwinding transformer wire is way less complicated than unwinding it from motors.
Even so, you might compromise insulation both ways.
We DIYers are pack rats and hate junking stuff 🙂
Same thing.
Hate to say this, being a pack rat myself, but most practical is to cut copper off and sell it by the pound (good $$$$) and selling iron on its own, way lessmoney but better than nothing.
Same with those motors.
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As far as cutting, I didn't mean I intended to cut the silicon steel. I was going by how the microwave oven transformers are assembled. That is, the "L" is welded to the "E" with a thin bead on either side. I intended to cut that thin bead with a hacksaw and just pry the "L" off. I've done that with the microwave transformers to make a welder. It turns out, however, that the low-voltage transformers aren't made the same way. The laminations on both sides are interleaved together and are coated with lacquer or varnish, so they don't come apart. Very interesting idea about the torch though. I may be able to gently burn that off and re-use the laminations. There's no way I can salvage the magnet wire from them though. I'd damage it for sure. The microwave transformers use cheap copper clad aluminum and it's all caked with lacquer/varnish, so that wire is basically useless to me aside from modest scrap prices. The motors are very useful however. I tap the core with a hammer on the opposite side of the bobbin and the core will spread open slightly. The bobbin then just falls right off. I then just spool the wire right off. I just finished winding a 400V toroid with it. Four parallel windings, so it should be beefy enough. I'm just making a small triode-powered headphone amp, so current needs aren't ridiculous. I had only planned on making a few chokes, so the prospect of printing bobbins isn't too daunting. I definitely wouldn't want to print 100 of them though, that's for sure.
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