Electronics > Projects, Designs, and Technical Stuff
Homemade IGBT MIG welder with ATX PSU parts. [blown yet again][blown count: 5]
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techman-001:

--- Quote from: Refrigerator on July 06, 2019, 11:09:14 am ---It blew up.  :-BROKE
Well, if failure is the best way of learning then I'm in for a whole lot of knowledge.  :palm:

--- End quote ---

I think failure is the ONLY way to learn, at least it always has been for me :)
magic:
Is there no way of gradually ramping the power up and watching the waveforms on a scope?
Refrigerator:
Slight change of plan.
I cracked open a failed (but genuine) RJK5010 MOSFET (20A, 500V) and it has a die size of 6x6mm = 36mm2.
Assuming that 20A/36mm2 = 0.55(5)A/mm2 then the IGBTs i had would be 12.25mm2 * 0.55(5)A/mm2 = 6.8A (yikes).
6.8A is a far cry from the advertised 20A so i will not even try to plug these back in but rather i'll go the MOSFET route.
BTW i knew the IGBTs were not genuine but i didn't think they were THIS bad (i expected something like 10A).
My Toshiba MOSFETS, on the other hand, are genuine, i know because i pulled them from a LG plasma TV.
They're 2SK2698 (500V, 15A, 0.35Ω), i had four but used one to replace the blown RJK5010 mentioned above (and fixed a plasma TV  :) ).
So i'll have only one per side but that's not a problem as long as my gate drive is correct.

I also checked the switching transistors from the ATX power supplies i took apart and they're like 10 or 12A rated so in theory using them would have been better than the fake IGBT's!

I actually might make another welder just to test these transistors out, mini spot welder for battery tabs perhaps?
Refrigerator:

--- Quote from: magic on July 06, 2019, 11:42:10 am ---Is there no way of gradually ramping the power up and watching the waveforms on a scope?

--- End quote ---
My scope only goes to 50V max (10x probe) but i do have a small variac that i will use for my second test.
strawberry:
RC snubbers for IGBT and rectifier
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