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Post by lamazoid on Jun 16, 2017 11:31:33 GMT -8
boost converter prototype
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Post by lamazoid on Jun 17, 2017 2:15:04 GMT -8
first welds. definitely not the best weld i ever made (lol) but it shows we're on the right track. the arc starts easily, just like on regular DC welder, and keeps running with whistling sound, like on SAT-1 video of course, it can be clearly seen that welding current is too low. so, our first point to improve is increasing boost converter power. Gary, i'm starting to think about your E-cores
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Post by tolik212 on Jun 17, 2017 2:25:05 GMT -8
Gary, can you to tell us some more about you cores ? What is ferrite material they are made from ? What is central tap diameter ? Window dimensions ?
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Post by lamazoid on Jun 17, 2017 3:41:01 GMT -8
added some output capacitance (470uF instead of just 6.8uF) - works better, arc became stronger.
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dave
Junior Member
Posts: 56
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Post by dave on Jun 17, 2017 4:47:38 GMT -8
Lamazoid , starting to follow this with real interest , I am a welder by trade amongst other things . Keep going , don't be discouraged . It is my dream to have a hand held (1 electrode burn capacity say 2.5 mm rod ) welder , powered by batteries that is completely self sufficient . An Idea has been patented around 2000 . But no-one has realised anything as yet .....good luck on your quest .
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Post by Gary Lecomte on Jun 17, 2017 5:27:22 GMT -8
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Post by lamazoid on Jun 17, 2017 8:10:21 GMT -8
Here is the Data Sheet for these B66343 E Core Ferrites. as far as i can see from the foto, your core is ungapped ?
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Post by Gary Lecomte on Jun 17, 2017 9:39:39 GMT -8
Here is the Data Sheet for these B66343 E Core Ferrites. as far as i can see from the foto, your core is ungapped ? Yes but you can Gap Them.
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Post by lamazoid on Jun 17, 2017 11:26:10 GMT -8
increased booster power from about 120W to 190W. MUCH better. it seems to be direct relation here. my estimation is - we need roughly 400W for 2mm rod.
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Post by Gary Lecomte on Jun 17, 2017 13:13:14 GMT -8
increased booster power from about 120W to 190W. MUCH better. it seems to be direct relation here. my estimation is - we need roughly 400W for 2mm rod. I use Many different ferrite cores that are NOT Gapped by the manufacturer. I just Gap them with Either a Piece of Mica or some Heat Resistant Transformer Tape. Usually I gap them with 0.03 mm thick piece on each leg of the ferrite. Sometimes a thicker piece, 0.06 mm of "Nomex Paper", used in transformer construction. I can also supply you with One Bobbin for this E Core.
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Post by tolik212 on Jun 21, 2017 0:06:04 GMT -8
I think, for welding currents piece of mica or tape isn't enough. Usage of grinding looks to be the way to go.
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Post by Gary Lecomte on Jun 21, 2017 5:34:31 GMT -8
I think, for welding currents piece of mica or tape isn't enough. Usage of grinding looks to be the way to go. What has the Welding Current got to do with Gapping? I have made some Very High Current Transformers with these E Cores, just using the transformer tape. However the Mica and Nomex create a more stable gap width. However from a stand point of Mass Production it is Easier to just order Pre-Gapped Cores.
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Post by lamazoid on Jun 21, 2017 7:59:56 GMT -8
I think, for welding currents piece of mica or tape isn't enough. Usage of grinding looks to be the way to go. What has the Welding Current got to do with Gapping? I have made some Very High Current Transformers with these E Cores, just using the transformer tape. However the Mica and Nomex create a more stable gap width. i think, Tolik is trying to say, that it's hard to get required GAP just by adding pieces of tape or nomex. also, this method leads to gapping entire core, instead of just central section, which results in high magnetic dissipation (i'm not sure if that's correct term, but it's called so in Russian). for the above prototype, i've GRINDED central part of the core to make an ~1,5mm gap. yeah, it's very large, but there was no other way to get target inductance of less than 10uH (actually ~7uH). at 24.5Khz with about 80% duty this gives out roughly 240W output. I think power ferrite cores are not the best choice for that task. Now i'm gonna experiment with iron powder toroid cores. will keep you informed.
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Post by tolik212 on Jun 21, 2017 10:38:34 GMT -8
In addition, such large gap can to became a source of another problem - that leakage of magnetic field, that causes massive heat dissipation in wire near the gap. 1.5mm of gap is red line, that if crossed - the problem above is on the way. There is an elegant solution I saw in EPCOS catalogue: distributed air gap. Yeah, the principle of powder cores applied to ferrites. The central tap is build from pieces of ferrite (just like rod), and non magnetic gap formers - spacers. Such way, EPCOS capable to create cores with low inductance, while still not suffering from magnetic leakage, and problems issued by it. It needless to say that implementation of that method requires not just grinding machine, but really experienced operator in addition.
But Lamazoid has another project, where this core will be capable to shine - welding machine based on full bridge topology.
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Post by Gary Lecomte on Jun 22, 2017 7:02:35 GMT -8
1.5 mm is Definitely an Excessive LARGE GAP.
A 0.06 mm Piece of material, Just placed on the Two Outer rectangles will create a more suitable 0.06 mm gap on the round center pole. Simple and No Grinding.
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