So, does this one look odd, or what!!
It's an antiquated system, which is almost never used here in North America [only in real old areas where the customer still requires it].
It is derived from a 3 phase 3 wire closed delta primary [the primary on the line drawing is the side with referenced phases as "A", "B" and "C" - plus it is the delta triangle on the pictorial drawing].
The secondary coils need to have center taps and 86% taps [depending on the placement] - this creates voltages as required.
The secondaries are:
Phase 1 [consists of two wires, or "A" and "B" lines],
Phase 2 [consists of two wires, like Phase 1 does].
Each phase is a 1 phase 2 wire output.
The phase offset [degree of time lag] between Phase 1 and Phase 2 is 90 degrees.
Secondary values [KVA, EMFs and etc.] for polyphase loads [between Phase 1's "A" and Phase 2's "B", or vice verse] are 1.414 x the values of one stand alone phase.
If the output voltage per phase [between "A" and "B" on a certain phase] is 100 volts, then the phase to phase voltage [between A from Phase 1 and B from Phase 2] will be 141.4 volts.
Once again, if we look at only one phase of this system's output, there's only one individual phase [wave form].
There's only a phase displacement between the two separate phase outputs.
I would guess that if you want to make the system grounded, just pick one wire from only one phase [just one line, or coil end should be grounded - else the smoke gets let out
] and bond it to ground.
Phase to phase voltage will remain the same, but if for instance we ground "A" from Phase 1, then there's going to be 100 volts to ground from "B" on phase 1, 141.4 volts to ground from "B" on phase 2, and who knows what from "A" on phase 2 to ground [looks like it could be either zero, 112, or 86 volts]. I'll need to check this one in the good 'ol EE manual.
Now, as to this being a 4 phase system - when compared to a 6 or 9 phase system, I've heard this system misquoted as just that - a 4 phase 4 wire system. Once again, it did no harm, so no big deal for the inaccuracy.
If there was 2 sets of 4 wire outputs, then it would be a 4 phase transformer.
Not really sure what the 'Taylor" guy's first name is [wouldn't that be an absolute laugh if it was Scott E. Taylor - it would be kind of close..].
There is the "Scott - T" connection for 2 phase 3 and 4 wire - derived from open deltas connected in Tee, instead of Vee. Maybe the guy's name is Scott!!
I'm gonna have to log off now. Must get up early in the AM and go all over everywhere.
I'll try to respond to the other posts about the transformers in this forum tomorrow.
Scott SET - babbling a specialty