[DragnsBane]

I need some help on how to convert 300 amps DC to AC current. I was given a 300 amp DC generator and would like to build a portable welder with both AC and DC welding capabilities. Any help would be appreciated.

[TinkerDJ]

You would need to build an inverter. There should be some plans somewhere. 300 amp dc generator, at what voltage. That actually sounds pretty interesting.

[2muchstuff]

I take it that you have a rotary generator, one that is to be driven by an electric motor or gas engine? If it is a true dc generator then it will take a fair amount of electronics to get 300 amps ac out of it ie: inverter. It could be an ac generator (alternator) with diodes internally mounted to convert it to dc. If that is the case, your in luck, just tap off before the diodes. I don't want to sound too negitive but to drive this generator to it's full capacity, I would guess about 12 to 15 hp at least. Almost sounds like a truck mounted unit.

[DragnsBane]

I took a good look at the generator this morning and here is what I could find out. It is rated at 300 amps continuous duty at 28.5 volts DC. I also talked to my father-in-law who gave it to me and he said he bought it from Surplus Center to do exactly what I want to do. I looked on Surplus Center and it appears that it is government surplus so I don't now if it has diodes in it. I have a 30 horse Wisconsin engine I rebuilt sitting in my basement so driving it won't be a problem. I have an arc stabalizer to go with it. I also have the plans to build a high frequency box for it. I just need to convert the DC to AC so I can have high frequency AC TIG capabilities. I'll have to open it up to see if there are diodes in it.

[Al_The_Man]

If you can see armature bars under the brushes, then it is DC, if it has slip rings (complete circle rings) for the brushes, it is AC.
If you are going to build a high frequency system, this usually start out with a DC supply, so why not go direct from DC to High frequency?
Al

[DragnsBane]

I might just do that Al. I wanted to have AC capabilities but this is supposed to be a "on the cheap" project. I know anything that can be welded with AC can be welded with DC and DC has the advantage of being able to weld a few things AC can't. It might actually work out better that way.

[harolda]

Bud you have a p2 aircraft genarator ? I know you have a aircraft gen.
The arc stabalizer is a frame with a coil of wire . The gen is dc no doubt.

Been there done that. Did not weld anything.Dont no why .It may
require 4000 5000 rpm

[BOB F]

If its aircraft gen; my dad made an engine driven welding generator from that. It works a very professional result. But be sure you have correct pulley ratio and engine governor has to be pretty well reactive. It runs at higher rpm so belt drive helps absorb intermittent load unlike in aircraft application where it is continuous.