I have searched for specs through all the data manuals at my work and an
indepth with Google but no luck.

Coded PRX1210620200 anode=stud. There is no id of manufacturer but it could
be SEMIKRON. Dimensionally the measurement across the flats is 1.25" and the
thread section is diameter 0.75". This is a monster of a device.

Recovered from a massive old UPS (3 tons worth) that once ran the whole
building during cutover to generator.

I'm intersted in building an arc welder (MIG or TIG) with these once i know
the spec....

Thanks

Pete

Coded PRX1210620200 anode=stud. There is no id of manufacturer but it could
be SEMIKRON. Dimensionally the measurement across the flats is 1.25" and the
thread section is diameter 0.75". This is a monster of a device.

Recovered from a massive old UPS (3 tons worth) that once ran the whole
building during cutover to generator.

Maybe 500A @ 400V (or higher V)? - Or 200-300A?

The physical dimensions seem to match the Semikron SKN 240 device:
http://www.semikron.com/databook/08rediod/n240.pdf

In the above pdf the hex mounting dimension is shown as across the
peaks rather than across the flats of the device. I have an older pdf
that shows the same dimension (SW32 - 32mm = 1.26") as being taken
across the flats. Comparing the drawings of each device it seems to be a
minor production change. My older pdf was for the smaller 45/70/71
lineup but it had the drawings for larger devices. Thats how I got
interested

The current pdf shows the devices as 400-1800V where the older range
was 400-1600V - not that it matters much for welding

Their current selection of rectifier diodes appears on:
http://www.semikron.com/skcweb/e/pro...rectifier.html

Looking at the next smaller & larger devices shows that only the "240"
was/is produced with a 3/4" stud.

Hmmm... the PRX prefix... About a year back I got some parts off a
MRI machine. Some more big stuff... All mounted on/between water cooled
copper blocks - & some of the parts were stud-mount diodes (SKR 71/04) -
thats why I had the pdf.

One of the MRI devices was a full-wave-bridge set of hockey-puck
transistors, PRX-D7ST402010KE. I never did find any data on them.

But I did find PRX is Powerex - http://www.pwrx.com/ - I think...

OK - The dimensions match a Powerex R610, 200-300A:
http://www.pwrx.com/pwrx/docs/r610.pdf

A e-mail request _may_ get you a data sheet on that p/n.

Instead of deleting the Semikron info I'll leave it in so you have a
choice of data - hahaha - If Powerex will get you a datasheet on the
real p/n that would be best!

With a adjustable HV source & a current limiting resistor you can find
the breakdown voltage of each diode & de-rate that to get a guess on
working voltage.

Good luck - Kim