Dnk - I think that although we are talking about a 3 phase system overall, the 120/240V 1Ø 3W between L1 & L3 is, in essence, single phase power (disregarding L2 and the other 2 transformers). Consider that single phase resi power is frequently also derived from 2 legs of a 3 phase system.
Anyway, the overall voltage between L1 and L3 (ØA & ØC) is 240V Single Phase with a grounded neutral connection at the centerpoint. IMHO there is little (if any) difference theory wise between this and a resi system.
I see what you're saying, if you connected the 3 line wires to a multi-trace O-scope, each sine wave would be 120º apart from the others. However, if you just look at L1 to L3 on a scope, you'd see a single 240VRMS sine wave, as there is but a single potential between L1 & L3.
Not sure I'm making sense here, please pass the gin. It's been a long week.
Radar
