phase difference on single phase residential services. 1

[bgisborn]

I've noticed that most texts show a 180 phase difference on the the two legs derived from a wye-delta 3 phase transformer when this is used for residential service. Forgive me, but I have a real lapse here. The 3 phases are 120 degrees out of phase with each other. Therefore it seems such a 3 phase derived 3 wire single phase service (assume grounded conductor is centrally tapped on one of the phases)should be 120 degrees out of phase with each other-not 180 degrees, which would give the fully balanced neutral current a value of 0. I know I'm missing something obvious but I can't seem to think of it.

 

[rbulsara]

See
thread237-110472

 

[jghrist]

A residential service derived from one center tapped winding of a wye-delta 3Ø transformer is a single-phase service. All voltages, both legs and the neutral are on the same winding and are electrically in-line. The neutral is halfway between the legs, so the voltage from neutral to one leg is 180 degrees from the voltage from neutral to the other leg.