Electronics > Projects, Designs, and Technical Stuff
Homemade IGBT MIG welder with ATX PSU parts. [blown yet again][blown count: 5]
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DannyTheGhost:

--- Quote from: Refrigerator on June 23, 2019, 10:06:57 am ---
Synchronous rectification would over-complicate things.

--- End quote ---

Sometimes you need to complicate your design when you don't want to dissipate over 50 watts from rectifier
MagicSmoker:

--- Quote from: xavier60 on June 22, 2019, 08:55:43 pm ---Interesting, I have been keeping alive a few Castolin/Eutectic PowerMax 2 welders that also have the phase shift topology. Maybe the same as the Miller.

--- End quote ---

My Miller was supposedly made by Fronius, but Fronius lost the contract with Miller soon after because it couldn't keep up with parts demand. I opened mine up to poke around inside even before the warranty was up and then again about a year ago to check the ESR of the elkos inside and everything was still within spec. Then again, I probably don't put more than about 10 hours of use on it any given year...



--- Quote from: xavier60 on June 23, 2019, 01:55:37 am ---I suspect that higher frequency makes the output choke unnecessary. I can't find the choke in the design the I linked earlier.
And my old welders don't have a choke. The rectifier output pulses are 100KHz, I think it relies on lead inductance.

--- End quote ---

The "choke" might be the leakage inductance of the transformer, usually by specifying an unusually large gap for a core that really shouldn't have one in the first place (e.g. - forward mode transformers). Note that this definitely falls in the "ugly hack" category, and not something I would personally try to replicate just to save on the cost/volume of a proper choke.

Refrigerator:
The transformer is wound, i took care to make sure the primary is properly isolated from the secondary.
Although as much as i tried i could only fit 7.5T in the secondary, no big deal.
I couldn't find appropriate litz wire for my primary so i went outside, screwed to screws into a board spaced about 1.7m apart and made some. In the end it was quite a squeeze but i think it looks pretty ok-ish.

Now i can begin building the primary switching circuit.
Refrigerator:

--- Quote from: DannyTheGhost on June 23, 2019, 10:28:43 am ---
--- Quote from: Refrigerator on June 23, 2019, 10:06:57 am ---
Synchronous rectification would over-complicate things.

--- End quote ---

Sometimes you need to complicate your design when you don't want to dissipate over 50 watts from rectifier

--- End quote ---

A CPU cooler can handle that no problem.
cur8xgo:

--- Quote from: Refrigerator on June 23, 2019, 01:10:11 pm ---The transformer is wound, i took care to make sure the primary is properly isolated from the secondary.
Although as much as i tried i could only fit 7.5T in the secondary, no big deal.
I couldn't find appropriate litz wire for my primary so i went outside, screwed to screws into a board spaced about 1.7m apart and made some. In the end it was quite a squeeze but i think it looks pretty ok-ish.

Now i can begin building the primary switching circuit.

--- End quote ---


very interested to see how that performs? so thats just magnet wire and you twisted it to make litz?

how did you decide on litz vs foil?

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