Originally Posted by
Flat_Bastard
I hate to be pedantic, but if you want to educate folks.
In AC systems you have, current "carrying conductors" ("hots"/black, red(120/240v 1phase), blue for 120/208V 3 phase, and brown, orange, yellow for 120/208v 3 phase and up), "grounded conductor" ("neutral"/white 120/240V 1 phase, gray 120/208V 3phase and up), and the "ground conductor" ("ground"/green 1phase/3phase).
If you loose the grounded conductor, you no longer have a path back to ground, or an open circuit. So no path for the electrons to flow.
If you loose the ground conductor, you still have a closed circuit, and a path back to ground. So the electrons will still flow.
In a balanced 240V circuit you don't need the grounded conductor for a return path. But if your machine has anything inside that runs off of 120V (think, the clock on your oven/range) you do need the grounded conductor, for the return path. So loosing your grounded conductor may very well shut the machine down. Though I am unaware of any welding/cutting machines setup like this, but I'm sure there are some out there.