If you have a delta supply, you should get the same reading between any two phases, You will not have any neutral.
If you have Star output, then there will be an equal reading between phases but there will be a centre connection tap that may or may not be brought out, you will get 50% reading from any phase to this star point.
If you require a neutral, this would be it, but ideally it should be grounded at the transformer, Check you local service supplier for the correct requirements, as some jurisdictions differ.
Depending on the star or delta, your phase voltage difference could be 208 or 220.
If you need 120vac 1 phase, then it may pay to set up a separate 1 phase transformer, with grounded neutral.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.