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

[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.