>> Occasionally day-dream about how I could make a stand-alone rectifier.
>> Practical advice appreciated.
>> Less and less need now with inverters getting better and better.
>> But no inverter I have yet met will run a 6010 "keyholing".
>> Rich Smith
> Start with the welder's maximum current, lets say 300A.
> The 300UR is reverse polarity. You need two electrically isolated
> heatsinks, the positive one for the two diodes whose threaded studs
> are cathodes and the negative one for the two that are
> anodes. Insulating the four diodes from a single grounded heatsink is
> possible but liable to hidden short circuits and the diodes will run > hotter.
> Large finned aluminium heatsinks are common cheap electrical scrap, if
> you know where to look. You may have to experiment to find how large a > fan it needs.
> The hardest part may be finding and fabricating heat-resistant
> electrical insulation that will withstand rough handling. I'd try
> unperforated FR4 unclad circuit board material rather than the temping
> PVC pipe. The high current terminals can be brass bolts through the
> insulation. I've found threaded copper starting motor terminals at a
> Diesel electrical shop and lathe-turned them into the high current
> studs I needed for a current measuring shunt.
> The housing for it can be a welded cube of angle iron with flat sides,
> if you don't have equipment to bend sheetmetal. Be sure that at least
> one side can be closed without access to the interior, i.e. tapped
> instead of clearance holes for the screws.
Jim - you said separate the four rectifiers of a bridge rectifier into
two pairs - because of their polarity? If I understand you rightly?
That would mean a practical welding rectifier could have two metallic
heat-sink assemblies separated in a glass-fibre (GRP) frame
Like the idea...
Should it be air-cooled or oil-cooled?
The one I used (probably 1960's or 1970's vintage) was air-cooled.