I too suspect that Kaos was involved with some level of design here, as it's operation is inverted [can't hear conversation inside but if your outside it's clear as a bell].

Plans most likely have Siegfried's PE stamp on them [Linked Image]

Having the split coils connected in parallel on this arrangement produces 120 VAC in that coil. Connecting all three individual transformers in a Wye configuration where the voltage of each transformer is 120 VAC will produce 208 VAC L-L / L-L-L, or 120 VAC to the common - this is the common method of creating a 208Y/120 VAC 3 phase 4 wire Wye system when using 3 common type 1 phase 120/240 VAC split coil transformers [Utility Companies' pole mounted xformer banks].

If the split coils were connected in series additive, the voltage of each transformer will be 240 VAC.
Now if we connect the 3 individual transformers in a Wye configuration where the voltage of each transformer is 240 VAC, the L-L / L-L-L voltage will now be 416 VAC, and of course the voltage from any one of the three transformers to the common will be 240 VAC.
This would be a 416Y/240 VAC 3 phase 4 wire Wye system.
If the common is not used, then the system would just be a 416VAC 3 phase 3 wire Wye.

BTW: Can you see how the pictorial "Y" schematic is made up of 3 individual transformers?? That's why I wanted to have the pictorial schematic drawn above the 1 line schematic - so there's a visual relationship to use.

Scott SET

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!