Running a 1-phase 240V welder off 3-phase 240V power receptacle?

[jakeru]

I have an Everlast Super200P. It uses 1-phase 240V input power. (2 live 240VAC conductors, and one equipment grounding conductor.)

I was wondering if anyone knows if I can wire an adapter to operate this welding machine off of a 3-phase 240V receptacle?

The 3-phase receptacle I would like to run my welder off of is a NEMA-L15-20R

(pic from: http://www.powerfig.com/nema-locking-chart.aspx )

I only need to TIG weld some .040" stainless using this. (Probably won't be drawing a large amount of current.)

Thanks!

[Ray]

Are you sure it's 240V, 240-3 is rare, it's more likely 208 or 220.
I sent you a PM.

[Steveg]

Why not. Just use any two of the hot wires and the ground wire, ignore the other hot wire. Three phase can be either 208 or 240 or some other voltage depending on how you tap the transformer.

sg

[jakeru]

I haven't taken any voltage readings off the receptacle, but next time I am at the work site, (if I do move forward with this job, anyway), I will do so.

The face of the NEMA plug/receptacle has "250V" embossed on it, but I could see that being a "max allowable" and not necessary indicate the typical voltage. But I'm kind of hoping/anticipating it would be 230-240V.

Based on some old welding machine specs I found I had printed out, I wonder if my machine might even be able to handle 208V if that's what I find?
"AC220 +/- 15% 50/60Hz"
I am not 100% certain these are the right specs for this machine (Everlast Super200P) or not. But if so, it would seem to mean the machine could run off a fairly wide, 187V-253V operating range.

[performance]

Actually Ray,
240 is not rare in 3 phase. It is very common in my neck of the woods. 208 is almost non existent, and found in many "older" installations.

Jake to determine the type of 3 phase you have, you need to measure leg to leg and then measure leg to ground.

240 Delta has a "wild" leg that will measure approx 220-240 across the leg but measure something like 277 to ground while the other legs measure 115 or so to ground.

You need to use the 2 legs that measure 115 volts to ground for leg to leg, Not a 115 and 277 leg even though they measure 220 across the terminals.

[Ray]

Thanks Mark, mostly 208 here from what I’ve seen.
Jake the markings on the outlet are the NEMA Ratings only. Really has no bearing on what’s actually there other than the installers willingness to follow code. Check it. You’d be amazed at what I’ve found/seen.

[jakeru]

Thanks for the tips guys. It sounds like I can work off of this receptacle then, provided that the voltage is in an acceptable range, and I don't overload the circuit.

Also, thanks Mark about the tip about testing for and avoiding using the "wild" leg, if I do find one. If all three legs have equal voltage to ground, I guess it would mean the circuit is driven by the other ("Wye/Star"?) type of 3-phase transformer.

I already mentioned to Ray that there was some type of free-standing, industrial dough mixing machine plugged into this receptacle. Kind of like a KitchenAid on steroids.

[everlastsupport]

If L1 is 120vac to ground and L2 is 120vac to ground, they are 120 degree out of phase, not 180 degrees like standard single phase power.

Not sure what the power supply will think about that.

Maybe you can rent a good (AVR or diesel) generator, or this can be a good excuse to buy one.

Did you look for 110vac outlets in the place like we talked about and tried to trace them to a panel with 220? In commercial buildings, I see 220vac 1PH separate from the 208, 277, 480 all the time.

[Rivets]

If L1 is 120vac to ground and L2 is 120vac to ground, they are 120 degree out of phase, not 180 degrees like standard single phase power.

Not sure what the power supply will think about that.

Maybe you can rent a good (AVR or diesel) generator, or this can be a good excuse to buy one.

Did you look for 110vac outlets in the place like we talked about and tried to trace them to a panel with 220? In commercial buildings, I see 220vac 1PH separate from the 208, 277, 480 all the time.

Hi Mike,

L1 - L2 is only one phase. So is L2 - L3, and L3 - L1.

The 240 volt, 120 degree 3 phase relationship only comes into play when the single phases above are interconnected to a suitable load eg. a 3 phase motor. It has to be that way, because each terminal pair above is connected across a single transformer winding.

So, the 240 volt welder power supply will only see one phase when connected to any one of the above 3 combinations.

Don't know about the "wild" leg.

Cheers,
Rivets

[sschefer]

Hi Mike,

L1 - L2 is only one phase. So is L2 - L3, and L3 - L1.

The 240 volt, 120 degree 3 phase relationship only comes into play when the single phases above are interconnected to a suitable load eg. a 3 phase motor. It has to be that way, because each terminal pair above is connected across a single transformer winding.

So, the 240 volt welder power supply will only see one phase when connected to any one of the above 3 combinations.

Don't know about the "wild" leg.

Cheers,
Rivets

Correct, and I've also never heard it called the "wild" leg but I have heard it refered to as "red high 208". I guess it all depends on your teacher.

[everlastsupport]

Hi Mike,

L1 - L2 is only one phase. So is L2 - L3, and L3 - L1.

The 240 volt, 120 degree 3 phase relationship only comes into play when the single phases above are interconnected to a suitable load eg. a 3 phase motor. It has to be that way, because each terminal pair above is connected across a single transformer winding.

So, the 240 volt welder power supply will only see one phase when connected to any one of the above 3 combinations.

Don't know about the "wild" leg.

Cheers,
Rivets

So how would he hook it up? You need two hot 110vac legs, 180 out of phase, that makes the 220vac, and a ground?

Probably best to get an electrician to confirm you have the above.

[sschefer]

So how would he hook it up? You need two hot 110vac legs, 180 out of phase, that makes the 220vac, and a ground?

Probably best to get an electrician to confirm you have the above.

Mike, in most of the U.S. 240V is two 120v legs, L1 and L2 off a center tap transformer. Both are of the same phase so a ground is not required to provide a difference in potential. The phase shift from - to + provides the difference. The ground is only for safety.

3 phase power isn't the most efficient but it does allow the use of smaller wire sizes and load distribution. 240 V 3-phase motors would be connected to L1, L2 and L3. Single-phase lighting would be connected L1 or L2 to neutral (N). No loads would be connected from L3 (the high or wild leg) to neutral, since the voltage would be 208 V.


So to answer the original question, Yes you can take L1 and L2 and make 208V but you will be operating at 75% of your power if your machine is designed for 240v. I've seen some strange things done to try and make 240 out of three phase but most often it results in damaged equipment and wiring.

[Rivets]

So how would he hook it up? You need two hot 110vac legs, 180 out of phase, that makes the 220vac, and a ground?

Probably best to get an electrician to confirm you have the above.

Mike,

On a 3 phase 240 volt DELTA circuit, there are no 120 volt legs. Just 240 volts across any Leg Pair. So that's how I would hook it up.

If the 3 phase panel provides 120 volt (Leg to common) outlets, then it's a STAR circuit and the Leg Pairs provide 208 volts not 240.

For safety, a ground is obviously needed. Just not familiar with this "wild leg" thing, but easy enough to check. I just don't have access to 3 phase mains ATM.

And yes, by all means anyone not comfortable with power MUST consult an electrician. Your point is well taken.

Cheers,
Rivets

[Steveg]

Rivets is correct. Use L1 and L2, L2 and L3 or L1 and L3. This so called wild leg is the voltage measured from L3 to ground on a delta circuit. This will measure 200 or better volts not 110V. My terminology for this is "high leg".

sg

[Rivets]

Hey Jakeru,

Did you succeed in hooking up your unit to one of the 240 volt phases ?
How did it work out for you ?

Cheers,
Rivets

[performance]

High leg....Bastard Leg...Wild Leg...I have heard several terms for this.

[everlastsupport]

Ken,

Thanks for a great answer and a proper solution. No ground IS a major safety issue.

I still would think there is 110volts somewhere in the place that will lead back to a 110/220 panel.

[Ray]

What I’ve seen around here is a utility owned transformer ether just inside the shop / building or outside around where the service comes in, for the 220V (110X2) service. Don’t think I’ve seen anywhere without some single phase, possibly in some factory maybe where everything is 480V.

[Ole Sarge]

Ken,

Thanks for a great answer and a proper solution. No ground IS a major safety issue.

I still would think there is 110volts somewhere in the place that will lead back to a 110/220 panel.

Minor, but it is actually 120/240. Power comes from a single phase transformer that is center taped, thus 120 X 2 = 240

[Ole Sarge]

Most commercial building are Delta, Y usually is speced where installed equipment needs 120/208, often times they will simply install a Y transformer inside the building. The 120 on a Y will be derived by going from a hot leg to the center tap on Y, which will have a neutral and ground tied to it. The neutral is a current carrying conductor, the ground is not, it is a safety ground and will only carry current in a fault condition, other wise it should never have any current on it.

Simple test to tell if you have delta on three phase is to read hot to hot, get 240, it is delta, 208 and it is Y. This does not apply to single phase 240. A Delta can provide 120/240, they simple use one of the hot legs, center tap it and you get 120/240.

Haven't heard of the star reference used before, but that would be a Y transformer output.

On delta their is more then one way to skin a cat, the grounds can also come off a hot leg in some situations. Knowledge on Delta is limited, I am mostly a Y kinda person.

Not an electrician, worked on high wattage UPS equipment. In any case on delta the ground is derived from center taping one of the legs, makes for some interesting voltage readings, with a 240, you can see voltages up in the high threes or 400 volt range.