On 08/05/2020 10:23, Richard Smith wrote:
"Richard Smith" wrote in message ...

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

https://www.electronics-notes.com/ar...-rectifier.php

Start with the welder's maximum current, lets say 300A.
https://www.digikey.com/product-deta...0U60A-ND/80681
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.

https://www.dummies.com/programming/...onents-diodes/

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.
Calling Jim, and anyone else who can help.

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
(insulating)?

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.

Regards,
Rich Smith

My Maxarc rectifier unit is air cooled and no fan either, the cooling of
the heatsinks and inductor being by natural convection. I could ask my
mate who has it at the moment to pull to cover and takes some pics if
necessary.