You’re correct, phase-to-phase is 173.2% of the phase-to-neutral voltage in 3-phase “Wye” service.
But that’s not what consumers (typically) use in North America. We don’t bring three phase to the home.
Our single-phase final distribution transformers have a center tap on the secondary coil, bonded to neutral. So, one side of the coil provides a 120v leg with respect to that neutral, and the other side provides an opposing leg, 180° from the first, and 120v with respect to that same neutral. Most of our appliances use leg-to-neutral, 120v. But leg-to-leg is 240v.
(Commercial and industrial facilities can get a wide variety of voltages in single or three phase, and we do have some actual, 2-phase generators and customers: the phases are 90° apart rather than 120° or 180°)
You’re correct, phase-to-phase is 173.2% of the phase-to-neutral voltage in 3-phase “Wye” service.
But that’s not what consumers (typically) use in North America. We don’t bring three phase to the home.
Our single-phase final distribution transformers have a center tap on the secondary coil, bonded to neutral. So, one side of the coil provides a 120v leg with respect to that neutral, and the other side provides an opposing leg, 180° from the first, and 120v with respect to that same neutral. Most of our appliances use leg-to-neutral, 120v. But leg-to-leg is 240v.
(Commercial and industrial facilities can get a wide variety of voltages in single or three phase, and we do have some actual, 2-phase generators and customers: the phases are 90° apart rather than 120° or 180°)