Ferrari Mailing List: Re: [NFC] Running a single-phase welder on 3-phase power

[Fellippe Galletta (fellippe.galletta]

In a true delta, the phase voltage (line to neutral) should be equal to the line to line voltage. 

Industrial plants often get what I call a "true" delta, because the delta services that feed homes are not one voltage -- most often a 120/208/240 VAC service.

You start with 240VAC, center tap the transformer to get 120 VAC. Then one of the lines will be sqrt (3) times 120 which brings you to 208 VAC. 

I'd measure the voltages to get an idea. Also a true delta should not have a neutral, only wye does. 

Of course if you can actually see the wiring configuration, it should be a snap to compare delta vs. wye. 

And yes, single phase that's a double pole (and not single pole) breaker should have two line conductors (or "hots" as the electricians call it) powering it.

FG

On Thu, May 7, 2015 at 3:02 PM, Rick Moseley <ramosel [at] pacbell.net> wrote:

Peter,

You should be just fine.  Were you working with a motor you'd have to be concerned with which legs you picked so you'd get the phasing right but with an older welder no issue.  Each of the phases acts a neutral for each other when the phase shifts.

That said, not knowing if your source is delta or Y, you could get an awful imbalance when you load the circuit.  If you can monitor your two hot legs while the welder is cooking and see consistent voltages, you are OK.   If not, play around with which two you use and try to get the best balance when under load.

Rick

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From: Peter Rychel <dino308gt4 [at] hotmail.com>
To: Rick Moseley <ramosel [at] pacbell.net>
Cc: The FerrariList <ferrari [at] ferrarilist.com>
Sent: Thursday, May 7, 2015 11:40 AM
Subject: [Ferrari] [NFC] Running a single-phase welder on 3-phase power

I wired this up last night at work and it runs fine, but want to post this and get feedback to see if I did this properly.

I work at a heavy industrial shop and all of the other TIG welding machines were being used. When our sister shop was shut down last year, we inherited their equipment and stock and I noticed an old Lincoln TIG/stick welder in the pile of junk. Last night I was in a crunch to get a TIG job done and I remembered that one, but when I pulled it out, I noticed on the panel that it was rated for 575V at SINGLE phase. Our shop uses THREE phase power.

I checked our outlets and if I measure from ground to one of the terminals, I get 300-some odd volts and if I measure from terminal to terminal, I get 600V.

From what I could gather from Google searching, if I omitted the one lead from the power cable (so, on the machine, only Green, Black and White versus the three phase cable of Green, Black, White and RED), it should work. My Miller Dynasty TIG machine I have at home is like that, you can run it on single phase power by just not connecting the forth, red lead of a three phase outlet.

I wired it up that way and it worked fine, but there were some notes that I read that it works, but is hard on the machine transformer. Is that true? Considering this is surplus equipment, it will only be used in emergency situations like this and is not going to be run during both shifts, day after day.

Peter

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