Crap Diodes! The truth about the 150EBU04 eBay special.
I recently finished making an inverter MIG welder but as soon as I tested it out the damn thing blew apart. Now why is that? One could say that I'm dumb and unable to make a proper welder but it's actually not that (not this time at least). The welder had previously underwent testing and worked flawlessly but all the testing was done on 12V. As soon as I tried pulling the trigger on 230V it blew three of the four primary switching IGBTs. At first I assumed the IGBT's were the problem, but when I rebuilt the switching stage with MOSFETs I still had nothing on the output. This made me question the secondary rectifier diodes, a quick diode test with the DMM revealed that they were all shorted, seems weird since the welder was unloaded so no current should have been flowing through the diodes. The diodes were marked 150EBU04 and they were supposed to be 150A, 400V diodes but as it turned out they were far from that. Considering I got them from eBay this isn't entire