Hello, all, and after studying the following pic at
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the wiring doesn't seem right. There appear to be two autotransformer boosters at either end of the mounting platform with a conventional transformer in between. The transformer primaries are apparently wired in delta but the secondary connections don't seem to make sense. (A configuration of three booster transformers (one for each phase) would seem more appropriate.) I can't seem to construct a phasor diagram of the wiring shown in the photo and none of my EE handbooks shows anything like this.
With these components I could connect the taps of the two boosters as open delta then close the delta with the secondary of the conventional transformer (assuming it has the appropriate turns ratio). But that isn't the wiring shown in the photo. There also appears to be 4 wires going from the transformers vice 3 wires going to the feeders at the top of the utility poles. Your time and comment is appreciated.