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Homemade IGBT MIG welder with ATX PSU parts. [blown yet again][blown count: 5]
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Refrigerator:
Found another degaussing coil laying around and this one is huge, only about 5.5mm thick (5-ish mm without the tape) but boy is it long and according to the link below it should be able to handle well over 50A and since i'll be using two secondaries it should be enough.
http://www.jst.fr/doc/jst/pdf/current_rating.pdf

Also i think i'll be doing a modified interleave winding with the primary sandwiched between my secondaries.




--- Quote from: cur8xgo on June 22, 2019, 08:23:03 pm ---
--- Quote from: Refrigerator on June 22, 2019, 07:55:23 pm ---Did some calculations with an online calculator and i think i'll settle for a 10T primary and an 8T secondary.

--- End quote ---

What kind of open circuit voltage do you get with a 10:8 ratio on a 240VAC rectified input?


--- End quote ---

Open circuit voltage doesn't matter because PWM. Also because of the way SMPS PSU works you have to divide your 230VAC peak voltage by 2.
A 10:8 ratio would mean about 17% duty cycle at idle to get 22V.
230*1.41 = 324V(peak)
324*8/10 = 259V
259/2 = 130V
22/130 = 17% duty cycle.

Actually 17% duty cycle seems pretty low, i hope my peak current doesn't get too high.
xavier60:
There happens to be a nice design for a 2 switch IGBT welder in this thread. https://www.eevblog.com/forum/beginners/component-role-in-a-circuit/msg2502276/#msg2502276
It uses the UC3845 current mode controller IC which is better suited than the TL494.


--- Quote from: MagicSmoker on June 22, 2019, 01:55:14 pm --- I have a cute little Miller inverter TIG/stick welder that is almost 20 years old (!) and still working great. It is a real work of art inside and uses a phase-shifted full bridge topology; something that was still very much considered "experimental" at the time.

--- End quote ---
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.
https://www.elektroda.pl/rtvforum/topic2554501.html
https://www.mig-welding.co.uk/forum/threads/eutectic-powermax-2-faulty.36400/
cur8xgo:

--- Quote ---Open circuit voltage doesn't matter because PWM.

--- End quote ---

There is an output choke right so thats why?

Refrigerator:

--- Quote from: cur8xgo on June 22, 2019, 09:19:40 pm ---
--- Quote ---Open circuit voltage doesn't matter because PWM.

--- End quote ---

There is an output choke right so thats why?

--- End quote ---

That and also some capacitors.


--- Quote from: xavier60 on June 22, 2019, 08:55:43 pm ---There happens to be a nice design for a 2 switch IGBT welder in this thread. https://www.eevblog.com/forum/beginners/component-role-in-a-circuit/msg2502276/#msg2502276
It uses the UC3845 current mode controller IC which is better suited than the TL494.


--- End quote ---

Yeah i've found quite a few of those:
https://www.hlektronika.gr/forum/showthread.php?t=53608
https://www.homemade-circuits.com/smps-welding-inverter-circuit/
http://danyk.cz/svar_en.html
 
But i want to make mine my way.
strawberry:
How about sinhronous rectifier?

modern IGBT can run 50..100kHz not just 20..30kHz

I think, bipolar gate drive is better than unipolar
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