Replacment Rectifier for MIG Welder

[MikeJohns]

I have a 250 Amp single pahase Mig Welder which had a diode short circuit in the rectifier.

The replacement rectifier was available but expensive and I didn’t really trust it already having had one die.

Stud mount power diodes were very expensive but after a little research I simply bought a few 50Amp diode rectifier blocks in alloy cases (CM5006) added a few for a large FOS and wired them all in parallel.. I mounted them on a common heasink for close thermal coupling and kept the lead lengths the same and it works very well.
The professional welder who was using my MIG machine thought it had a smoother arc than before it failed.

If anyone wants to produce a high current cheap rectifier for any purpose the diode blocks cost me around $8 each for 10 and I used 8 for good measure because I didn’t know how well it would work.

That gives a 100% duty cycle of 400A and they don’t even get warm at 180 Amps continuous , if I did it again I’d just divide the current by 50 and round up ( 5 blocks for 250Amps ) the rectifiers are already overrated and handle surge current an order of magnitude higher for short periods.

I'd also use crimp connectors too rather than soldering.