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This is a "three phase" system. Yet, when using two pole breakers, you may set them up as follows:
- 240 leg to 240 leg; in essence, similar to our usual 240 circuit; or,
- 240 leg to 0 leg; in essence, similar to our usual 120 circuit, but with double the volts.
Now, these two circuits cannot be equivalent, unless we are also somehow drawing current from the "0" leg. That would make for an interesting "neutral!"

1) Of course the _grounded_ conductor in this case is _not_ the neutral. With respect to the circuit and loads, it is the equivalent of the other phases. Think 'grounded phase'.

2) Even with a true neutral (say the mid-point of a wye connection) you _must_ be able to get current out of the neutral...the current flow at the neutral has to balance whatever is coming out of the other transformer terminals.

3) The grounding has nothing to do with the current flow from the transformer terminals. Any of these circuits would work just fine even if totally ungrounded. Corner grounded wye would work just fine; you could even come up with a bastard system where you connect a random transformer secondary to the neutral point on a wye, and ground the other side of that secondary, so that the 'neutral' is at 10KV to ground, with all of the 120V 'phases' at roughly 10KV to ground as well. It would be hell on the insulation system, but your standard 120V lamp would work just fine [Linked Image]

-Jon