What is an open wye? Which conductor is omitted, and with the omission, how does the system continue to be a wye?
Now that I think of it, the primary shown here should not differ, except in voltage, from a 120/208 single-phase "network" service. In such a case, you have 120 degree displacement, but you also have 120V to neutral from either phase, and 208V between phases. This is distinctly different from a corner-grounded delta, in which one phase is grounded and the other two are equal in potential with reference to each other and to the grounded phase.
I was always taught that a 3-wire 120/208 service is single-phase, but looking at this photo, and following the logic of the schematic, it seems there should be three phases there. I've never tried checking this with a scope.
Can anybody shed light on this?
