208v 3ph --> 240v 1ph ?!?

Many welders are now made for single and three phase pending a different cable installation inside...

Can you change cable and be in like flint ?

Otherwise your electrical type can install a transformer. Since you handle 200 ok - a single leg of 208 seems ok to me.

Martin

Mart> At work I will be needing 240v 1ph power for my plasma cutter, but all

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Your plasma cutter may work. My Hypertherm 1000 will lock onto many different voltages, 3 phase or 1 phase.

If it does require single phase voltage then you can start with any two leads of your 3 phase power and use a transformer to change the voltage to what you need.

Grant

Dan, Make certain that there are no neutral to ground references within the unit. You can use an ohm meter to do this. If you find an open circuit, then making a phase to phase reference for power will not be a problem. I do not believe the lower RMS voltage will make a difference. Steve

208 is on the low side of the range from 200 to 240, but it is well within the specified range so it should work OK.

I'd say "yes" as long as the "208" IS 200 volts or more. I think the specs for line voltages go something like "nominal + or - 10%". 208 -

10% could be 208 - 20.8 = 187.2 and still be in spec. I just googled "nominal line voltage" and got tired of poking around, but at least one site said that the spec is now "nominal +/- 5% instead of +/- 10%. One site even said that in the state of California "they" are requesting +/-2%. Just for the record (what I am saying, not what may be true) "nominal" used to be 117 and 234 for the common single phase entrance. That's a range of 105 to 129 for the 117 and a range of 211 to 264 for the 234. One could argue that 234 isn't the correct number for the thing we commonly call "220", but what else can you conlcude when all that's on the pole is a center tapped secondary transformer? ----And I sure remember well the taps we had to put on our equipment's transformers to make sure we could handle both 105 and 129.

Just rambling. Pete Stanaitis

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dan wrote:

I'm not sure I understand your question, or perhaps you don't understand the specs. You have a plasma cutter that accepts an input voltage range of 200v-240v and you have 120/208v Wye service available. Connect the plasma cutter input to two of the hot phases from your service panel i.e. 208v phase to phase, connect the safety ground and be done with it. The available voltage is entirely within the requirements of the plasma cutter.

It will work fine - 208V is within the rage of 200V - 240V. Much commercial gear is dual rated for this exact reason, though you'll notice that current draw goes up a bit and capacities go down a bit.

The only time you have to worry is when you have a 240V 3-Phase Open Delta "Wild Leg" or "High Leg" service, and even then you could connect the welder or cutter between any two of the three lines. But when connecting 120V loads to an Open Delta panel you can NOT connect them to the High Leg which is not 120V to ground or neutral, it is

208V. Usually coded in Orange, and you make a 3-phase connection Black-Orange-Red and MUST follow the same wiring everywhere.

Machine tools often have 120V work lights connected to the black or red. The Orange line will make them very bright for about a second.

This high voltage will quickly let the "Magic Smoke" out of any 120V light fixture ballasts or other gear, and when the factory installed supply of Magic Smoke escapes you have to replace the whole appliance.

If there's a "High Leg" warning on the panel cover they do mean it. And if it's hand lettered in permanent paint marker, it probably means I've been there before and changed out a few blown ballasts.

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What's that Lassie? You say that Pete C. fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Tue, 26 Aug 2008 11:21:08 -0500:

That is just what I wanted to know.

One more thing. Can I make up a L14-20P--> L6-20R pigtail that will plug into the outlet at work, that uses only two legs of the 3ph service and ground?

That would save me the trouble of having to have the electrician add an outlet.

What's that Lassie? You say that Bruce L. Bergman fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Tue, 26 Aug 2008 13:42:55 -0700:

I thought that might be the case when the in put spec was so wide.

We have real 3-phase at work, but I will check with a vom to be sure.

>

Open Delta is still "Real 3-Phase", it just has that High Leg to worry about for 120V loads. If your load is straight 240V it really doesn't matter, pick any two.

If you get 240V between any two legs of the three, and the Phase to Ground reads 120, 208, 120 you have Open Delta. Mark the High Leg orange, and never connect anything 120V to that phase.

If I wanted to really baffle you I'd bring up Corner-ground 3-Phase. That one even sends me scrambling for the books...

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What's that Lassie? You say that Bruce L. Bergman fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Fri, 29 Aug 2008 01:12:06 -0700:

I checked today and got 208v between all pairs, and 118v from each to ground.

Okay, you have 120/208 Wye - pick any two pairs you like.

Although if you wanted to be really pedantic, you could take a clamp ammeter and monitor the currents on all three phases at the Main Breaker, and shuffle around a few of the big loads to even out the current on all three phases.

But it usually comes out close enough to work fine at random, unless someone built the place and deliberately put all the big single-phase loads on A and B and never on B-C or C-A.

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