I think the two voltages in the subject line are the standard voltages for industrial use in the US. What I don't see is the connection between them. It seems that if you use a transformer bank consisting of standard 120/240V single phase transformers you could get 120/208 and 240/416V. I infer that the 277/480V transformers must be of a separate type, right? Is the 120V taken from the same transformer as the 277V or are these two entirely separate systems?

(I considered placing this message in the General area, but as it is theory to some degree it landed here.)