No, there is no transformer, just a 3 PH 4 wire 120/208, runs from a disco outside, into a large enclosure with CTs, then to an auxilary gutter. nippled to the gutter, are two panels. the main panel feed is tapped from the gutter, and the sub panel is fed from the main panel. The sub is fed from a 2 pole breaker in the main, on A and B phases. Sorry for the confusion, I have always called two legs of a 3 phase panel "single phase", guess it always reminded me of a 3 phase motor that lost a phase.
