# 500 amp bridge rectifiers for AC welder conversion



## cathead (Nov 11, 2019)

E-Bay has 500 ampere bridge rectifiers available from the far east for a little over 50 US dollars and 200, 300, and 400 amp bridge rectifiers for correspondingly
less money.  I went with the biggest rating one because it will be used for rough service for welding.  Anyway, I mounted a heavy aluminum plate an inch thick
to the back of the rectifier with some silicone heat transfer goo and bolted a large heat sink to that with more goo of course.  The biggest effort was so make
up a set of cables to wire up the rectifier.  Also I made a large smoothing inductor to add to the secondary circuit.  I'm using an old Forney 180 amp plug in welder
so had to machine tapered plug and socket ends to fit to the welder and existing welding cable.  To my amazement,  there is a huge difference between the old
Forney on AC and the Forney with the DC adapter rectifier and inductor.   It produced nice welds on both straight and reverse polarities.  Also I experimented
with leaving out the inductor and found that it was helpful in making smoother looking welds.  I also have an old Miller Generweld 130 AC welder that I would
like to try this rectifier set up on.  I need to mount the inductor and rectifier together and add a carrying handle to it and I will consider this project done.


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## Bi11Hudson (Nov 11, 2019)

An excellent way to upgrade a lower end welder. I made a similar conversion some 15 years ago and am quite pleased with the results. 

I used 1/2" copper pipe slit and pounded flat for bus bars. The diodes were salvaged from a DC crane power supply. (600 V 500 A) I figured though they wouldn't stand up on the crane, for a lighter load they still had some life left. A Lincoln 225 buzz box with copper windings that took some finagling to get every thing "clear" and still be adjustable. I did cheat a little and bought the connectors. My philosiphy is to keep everything I modify reversable to OEM build, just in case~~~ 

As an electrician, I am a little skepical of aluminium as a conductor, but I guess that's just the "old school" side of me. The internal fan was moved but still cools the transformer. I congratulate you on a wise decision to not just throw money at the problem, but to make "it" into what you need.

Bill Hudson​


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## cathead (Nov 11, 2019)

Bi11Hudson said:


> An excellent way to upgrade a lower end welder. I made a similar conversion some 15 years ago and am quite pleased with the results.
> 
> I used 1/2" copper pipe slit and pounded flat for bus bars. The diodes were salvaged from a DC crane power supply. (600 V 500 A) I figured though they wouldn't stand up on the crane, for a lighter load they still had some life left. A Lincoln 225 buzz box with copper windings that took some finagling to get every thing "clear" and still be adjustable. I did cheat a little and bought the connectors. My philosiphy is to keep everything I modify reversable to OEM build, just in case~~~
> 
> ...




Hi Bill, 

Thanks for the nice post!  I agree and don't think I would own a welder with aluminum windings.  I used 1/2" copper pipe to make
my cable ends by flattening one end and drilling a hole in the flat part.  I soldered the welding wire to the pipe tube end for a good connection.  
I made no modifications to my welder and can use my DC adapter on several machines if I want to.  When I get to using the DC function, 
I will monitor the temperature of the diode block and also the inductor to keep from cooking something.  I didn't notice any temperature rise
at all in my initial tests.


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