calling john t or janicholson electrical ????

[glennster]

picked up these two mig welders a while back at a sale. 400 amp units. they are 3 phase. can i run a rotary converter from 220v single phase to run one of these buggers?
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[MarkB_MI]

A better (and cheaper) solution is to change your welder over to single phase. If this is possible, it should be shown in the schematic diagram for your welder, which would be inside the welder. You can download the manual for your welder using the link below, but it doesn't show any provisions for conversion to single phase.

The problem you will have with your welder is that to operate at full rated output, it needs around 47 kVA, which at 240 volts single phase is almost 200 amps! A rotary converter that size is going to be big bucks.

You might be able to get it to work at maybe a third of its rated current off a single phase, but you would then have the world's heaviest 130 amp MIG welder.
R3S 400 Manual

 

[buicanddeere]

Maybe, maybe not.
I've seen "three phase welders" installed. And the hydro service updated to three phase from single pha$e. Or various versions of $ingle to three pha$e converter$ added.
Then.....................The time comes to run the three conductor plus a ground power cable to the welder. The welder's terminal box is opened and the ground is connected to the chassis lug.
Line 1 is connected to the 1st insulated lug.
Line 2 is connected to the 2nd insulated lug.
Line 3 is connected to the 3rd insulated lug..............wait a minute. There is no insulated 3rd lug??????????????
Turns out the welder is 208,240.480 or 600V SINGLE phase.
I have a mean mother 400amp AC/DC Hobart in the garage that any amateur can lay a near perfect bead with a 7018 rod on DC.
The terminal box in it can be wired similar to a multi-voltage AC motor. 240/480 or 600V, all single phase.

 

[buicanddeere]

Three phase equipment supplied with two legs of the three phase service will make 57.7% of it's rated power.

 

[John T]

Glen, I havent looked at any of the specs or manuals etc but just off the top of my head SURE if you wanna sink enough bucks you can buy a big enough rated (NOT cheap) 240 volt single phase rotary converter but this is lookin like a Rube Goldberg iffffffffffff you wanna get anywhere near the capacity that welder has to offer. As I'm sure youre aware it was designed for and used where 3 phase was avaialble and it can work pretty efficient at converting that crude AC energy into welding amps n heat buttttttttt if you rewire (if even possible) it n try to run it off single phase youre gonna suck up a bunch of juice even to get it to some precentage of its 3 phase capacity.

Without diggin into the manuals or specs Id say a converter is cost prohibitive while a single phase conversion is gonna take a lot of electricity and produce a bunch of heat n losses to weld anywhere near what it could do if 3 phase.

Its your bucks so check into a converter cuz I like that plan wayyyyyyyyy better then any single phase use if thats even possible....

John T

 

[glennster]

thanks john, kinda looks like i'll need a 3 phase drop put in. according to the link below, it likes 230 or 460 3 ph, 68 amp on the 230 side or 34 amps on the 460 side. ah well, i guess i can always put that grain leg in and a new drying bin, upgrade all my grin bins to 3 phase too!!!! geez what starts out as a really good deal sure gets spendy in a hurry!!!!!!!!

 

[John T]

But theres a silver lining, 3 phase equipment is more efficient and the motors are self starting and as youre already aware you can sometimes pick up 3 phase equipment cheap at auctions.......

John T

 

[buickanddeere]

glennster

Before doing anything else. Have a look in the terminal box to verify if the welder(s) are single phase or three phase.
Most get connected to "three phase" supply because they require 480 or 600V. Not because they need three live lines.

b&d

 

[MarkB_MI]

I stand corrected, B&D.

Actually, hooking his welder up to single phase might work if he only needs about 200 amps max. Looking at the schematic, the control circuits are powered off the L1 and L2 lugs, meaning one could tie 240 volts single phase to these two lugs, leaving L3 disconnected and the welder should still work.

 

[buickddeere]

mark

I'm not talking about connecting a three phase welder up to single phase.
I'm talking about welders that require 240,480 or 600V but only have two "live luggs" from the factory. The transformer inside only has two live input lines not three.
I see this all the time at work, everybody assumes the welder is three phase because it's plugged into a three phase 60amp 600V welding receptacle.
The welder uses only two live lines but uses 600V so a 100amp supply cable doesn't have to be dragged around.

 

[MarkB_MI]

Hi B&D,

I grok what you're saying. When it comes to three-phase machines, there's (at least) three varieties:

1. Welders that are really single-phase machines but everyone thinks that they're three-phase because they have a three-phase power cable. I frequently look for these on eBay, because they often go for a fraction of their real value.

2. Welders that have provisions for either three-phase or single-phase connections. Typically the input transformers are wired in parallel for single-phase, and wired delta or wye for three-phase.

3. Welders that were never intended by the manufacturer to be connected to single-phase power.

The particular machine we're talking about, a Lincoln R3S-400 falls into the third category. It's not supposed to be run on single phase. But is it possible? I think it is. Now I can think of a number of reasons why this would be a Bad Idea, such as the fact that the current draw on single phase would be phenomenal. But if I was in a bind, and had a choice of no welder, and jury-rigging a three-phase welder to run on single phase, I'd give the jury-rigged welder a shot. I'm sure this welder running on single phase would still weld circles around my 170 amp Lincoln, which overheats if you try to weld 1/4" steel for more than a couple of minutes straight.