How big of Rotary Phase Converter needed to run 3phase 315lx tig welder on one phase?

well anyone know? There isn't a single thread about the 315lx machine being used in this whole forum, so I'll be glad if I can get any response.
It looks like the machine draws 21 amps at 240v 3 phase which is around 7hp. Can I get buy with a 7hp RPC?
I don't really need 315 amps most of the time, all I need is 200A max. Mainly I'd like to buy a machine with AC frequency control to try out.

I know the 250ex is another option, but I can get a 315lx for about half the price. I'm guessing since few have 3 phase power that is the reason for the low price.

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Originally Posted by aluminumweld

well anyone know? There isn't a single thread about the 315lx machine being used in this whole forum, so I'll be glad if I can get any response.
It looks like the machine draws 21 amps at 240v 3 phase which is around 7hp. Can I get buy with a 7hp RPC?
I don't really need 315 amps most of the time, all I need is 200A max. Mainly I'd like to buy a machine with AC frequency control to try out.

I know the 250ex is another option, but I can get a 315lx for about half the price. I'm guessing since few have 3 phase power that is the reason for the low price.

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I do not believe a lot of testing has been done with RPCs and inverter welders. A lot depends on the quality of the converter and the control. A Phase Perfect unit should have no problem, but the cost is pretty high. American Rotary classes welders as a hard load, so probably 10HP minimum is a better choice. Equal phase voltage and angle are important to inverters, and the cost goes up as you get to that point. The 315LX is an older analog unit so it might not be as sensitive as something like the 325EXT. You can call support to see if they can give you any more info. Since this is mainly a hobbyist and light industrial forum, you wouldn't expect to find much 3 phase.

Call your electricity provider and see if they can bring 3 phase, I have three phase at home!

I would not use a rotary phase converter with a welder. If you do you would need a 15 hp rotary converter to do a decent job with it. Rotorys do not make very good power. I have a Phaseperfect digital converter and it will run any kind of 3 phase load but they are costly. I have a hydra shift lathe with a 7.5 hp motor and I would have needed a 15hp rotary converter to run it well. A 10hp minimum but there would have been limitations with it. I believe the smallest Phase perfect is 10 hp and it is about $3000. To me any welder under 300 amps there is no need for 3 phase. Even most industrial welders run 440 single phase. A rotary converter will about double your electrical usage for a given load. A phase perfect is 97-99% efficient and continually corrects for unity power.