Here's one of a 4 wire Wye, using three separate 1 phase transformers - as would be on a pole mounted transformer bank.
Note the complete difference in how the coils are wired here, as to the Delta method??
These coils [split coils] are in Parallel - so each transformer has 120 VAC output. On the Delta, each transformer's split coils are in series, so each transformer has 240 VAC output [the bottom coil is center tapped for the neutral].
Comments??
Scott SET - sorry for the text!!