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Switching inverter welders

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MorRobotz:
You ever look at the specs on these things?

I found this build log http://danyk.cz/svar_en.html
Crazy stuff.

I know you can buy Chinese ones for less then 300 bucks that do 90+ amps DC.

Anyone ever think about building their own? >:D It's been haunting me for a while now.  :-DMM

No need to lecture me about HC and HV safety. half of my dreams involve isolation slots and thermal cut offs. Other half of the dreams involve larger capacitor banks. Soo... thoughts?

MagicSmoker:
The site you linked to shows a two-switch forward converter - an excellent choice of topology overall due to the low stress on the primary switches and extreme ruggedness. There's a few things in the schematic that are a bit questionable/wonky, but nothing that is a show-stopper. Go ahead and build it.

NiHaoMike:
It would be very difficult, to say the least, to build one for less than the cost of buying one, especially after accounting for development time and blown components. Now if you're after something exotic that either doesn't exist on the market or is considerably more expensive, go for it. Even then, it might make more sense to modify an off the shelf device.

Miyuki:
Im now building one but more complex with pfc, full bridge topology and mcu controlled to generate "constant voltage" for GMAW
I have now done PFC module controlled by IR1155, but must be checked at load, AUX supply, its simple flyback to generate 2x12V and output rectifier which is bridge to simpler design, both sides of transformer is then clamped

to do:
Must write control software and put transistors to power stage and wound transformer and output inductor

najrao:

--- Quote from: MorRobotz on July 28, 2016, 07:29:58 pm ---You ever look at the specs on these things?

I found this build log http://danyk.cz/svar_en.html
Crazy stuff.

I know you can buy Chinese ones for less then 300 bucks that do 90+ amps DC.

Anyone ever think about building their own? >:D It's been haunting me for a while now.  :-DMM

No need to lecture me about HC and HV safety. half of my dreams involve isolation slots and thermal cut offs. Other half of the dreams involve larger capacitor banks. Soo... thoughts?

--- End quote ---

Old thread, but new to me!
I am considering repurposing telecom rectifiers as inverter welder. These are extremely well made, and very low cost in the local market. I have may be more than a dozen, of different ratings; the ones in contention are 54V 83A continuous. Also have 27V offerings if more suitable. Using three to be fed by 3-phase 400V, one in each phase, would make for an output of 250A!

Intended as lead acid battery charger, the rectifier has settable inverted L current limit, and a voltage adjust range of 42-59V: still needs to be studied for how to do these via the logic pins at the connector. On an older rectifier, which had somewhat more open layout, I have indeed modded to adjust CV and CC, zero up each. Pretty difficult because pcb's are multilayer, and with very small smd's, all in extremely compact packaging. The wide input range PFC would reduce current demand from the mains, as would 3-phase input (only for high power). Efficiencies are out of this world, 94% on the specification sheet. Resonant mode ZVS.

I should think I will still need an additional external inductor and freewheel, and do not know how to size these.

Just concept yet, so open to all suggestions. Will work on this if I have what it takes.

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