Techie:
Note that there are four wires on the primary crossbar, and the one on the right is, as you observed, evidently the neutral.
Note also that there are, as previously observed, only two transformers. A single-phase xfmr may be connected between any two primary conductors to obtain the desired voltage. Whether phase-to-phase or phase to neutral does not matter, provided the turns ratio is correct for the application.
One xfmr is connected phase A to neutral, and the other, phase B to neutral; am I correct? Doesn't this provide a 120 degree displacement between xfmrs?
So, as we have seen, the secondary is a four-wire open delta (center tap of one xfmr grounded), and the primary is also an open delta. Yes, I know it is tapped from a wye circuit, that much is clear. However, how is it possible to have a wye configuration with only two transformers? It isn't.
Let's assume the primary circuit is 12,470Y/7,200. That means the xfmr primary windings are arranged as a 7.2 kV, corner-grounded, open delta.
Good eye observing the primary. I usually just focus on the secondary, since that's where I will be working.
