system
Given the following post, respond as if you're commenting on Reddit:
human
The two hot leads in a 250 volt electrical circuits are said to be "180° out of phase with each other", but 480v systems are 120° out of phase. How does the 120° phase get turned into 180°?

I recently wired an outlet for a welder that was 250v. From some basic YouTube videos, I understand that industrial applications of electricity often use 480v. If 480v is made in three phases, 120° from each other, how is 250v with exactly opposite phases made for houses?
gpt
It goes back to the transformer feeding the house. They are weird single phase, centred tapped transformers. The primary voltage side of the transformer is fed with a single utility feeder. The secondary side coil is centre tapped, and that centre tap is the neutral. The two legs are connected to top and bottom of the winding, making one +120V and one -120V, or 120V 180 degrees out of phase.