Scott — Minor nit, here. 6,930 Vø∙n corresponds to 12,000 Vø∙ø. 13,800 Vø∙ø is associated with 7,970 Vø∙n. [Forgive me, Scott.]

Donald Beeman’s 1955 Industrial Power Systems Handbook recommended solidly grounded 208Y and solidly grounded or resistance-grounded 480Y for commercial/small-industrial building-distribution voltages. The book sort of ‘poo-pooed’ 240V ∆ as essentially ‘stone age’, but as we can see, ~50 years later there’s still a lot of it for small 3ø loads.

A modern iteration of Beeman is IEEE’s standard 141-1993, Recommended Practice for Electric Power Distribution for Industrial Plants {a/k/a the ‘Red Book’}.

Where 480Y is common below the 49th parallel, 600Y is equally status quo above the 49th. {208Y is popular on both sides—sort of an odd coincidence.} 120/240V 1ø 3w is extensively used in homes above and below 49°.

The 60Hz, 208 versus 240V ‘gap’ also shows up at 4.16-4.8, 12.0-13.8 (or 14.4) and 115-138kV levels on the North American continent. Voltage ratios of 2 and √3 seem to have evolved where inherently a factor of 2 relates to equal series/parallel windings and √3 relates to ø-ø/ø-n quantities.

[This message has been edited by Bjarney (edited 03-13-2004).]