Me either ;-) Brain fart
208/120
OK you have a regular 120/240 transformer connected to one phase of the medium voltage distribution (13kv or whatever) Then I add a second transformer from another phase and a 3d transformer from the last phase. I already have my ground in the first one so I will connect the secondaries in Delta. Voltage l/l around the triangle are 240v but I still have the original one that is still
120/240. That gives me the best of both worlds. Plenty of 240 3p and as much 120/240 as I size that transformer for. Now as was mentioned before, you can actually remove one of those transformers and it still works, with about a third less capacity on the 3p. Typically you will see two transformers, one big one and one smaller one. The big one is the 120/240.120 * 1.73 = 207.6 call it 208