Success i have just soldered everything and the welder is working.
Good news. I am pleased.
I was going to post to say the replacement IGBJT would be OK, in fact better, provided there was nothing onerous about the application, especially high frequency which IGBJTs are not good at. Did the faulty IGBJT go short circuit? That is the normal failure mode when the BJT juctions fuse due to excesive heat (temperature) and high current. It always amazes me what current high power semiconductors can handle.
In my limited experience, it is not uncommon for welder IGBJTs to blow; they have a hard time. Is there a good heat sink. If not perhaps think about fitting one to increase reliability- the bigger the better. There is a welder repair shop in Bath, UK where my son lives. I normally have a chat with the men working there when I am passing. They are knee deep in blown IGBJTs, especially from the cheap Ebay type welders.
60Khz sounds about right for an inverter welder. They use switch mode techniques with a relatively high frequency to make the transformer smaller and cheaper. The transformer size is inversly proportional to the frequency, for a given power. 'Transformer' welders (50Hz/60Hz), as you no doubt know, are big, heavy and expensive, but the most reliable.
As far as I can tell, for practical purposes, the schematic symbols you show for the two IGBJTs are the same and don't imply anything sinister, something I must investigate.
Intrested in your welding experience. What sort of stuff do you weld? Are you a professional? I have done quite a bit of ark, carbon arc brazing, and MIG, mostly cars (autos), but am dreaming about moving to TIG AC for welding ally too. TELWYN gear is good but w...a...y above my price range.
(PS: thks for 'like' vote- my tally is going up
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