On Mon, 18 Nov 2013 07:08:23 -0800 (PST), TimR
wrote:

On Monday, November 18, 2013 9:48:27 AM UTC-5, wrote:
Here's what I'm not getting at the moment. What are the connections to that transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I'm pretty sure it is.



All the neutrals are tied to ground. Why would you expect

the neutral on the secondary to not be at ground level?

In the strictist sense, if you take a center tap transformer,

the secondary side doesn't have to have any relationship

to the potential on the primary side. It's can be completely

seperate, it's a seperate winding not connected to the primary.

What and how you hook it up

determines what level anything is referenced to. In the power

transformer case, the center tap (neutral) is tied to ground.

Well, you're not seeing the problem. I wish I could draw here.

Your transformer has two wires going in, and three going out.

I don't know what primary is in my neighbor hood, let's say 2400 vac for an example. Which two wires do we use? You only have the choice of leg to leg, or leg to neutral.

Choose leg to neutral: use a 10 to 1 turns ratio, your secondary will be 240 volts line to line. Then center tap it, and you get 120 from each line to center.

Pick one. It doesn't matter.

BUT: why would center tap be anywhere near neutral?

Because that's how it's wired. You *DEFINED* it as being 0V and
connected it to ground.

Choose leg to leg: does the same problem exist?

No. There is no problem. Remember that transformers isolate. The
secondary can be at any voltage you desire it to be, regardless of the
primary (within the breakdown limits of the transformer, obviously).
You connected one of it's secondary terminals to ground, defining that
as 0V. Everything else falls out from there. You could have
connected it to 1000V, but that wouldn't be smart. ;-)

Once it gets into the house I understand how it works, but on the pole I'm hazy.

There isn't any difference how it's connected there. You may have
heard of "Delta" or "Wye" connections. Delta, connects the primary of
the transformer between phases. A "Wye" connection would be from
phase to ground. In the US, almost all loads are connected as "Wyes"
and generators as "Deltas". I'm sure there are exceptions but that's
what you'll find on your pole.

By the way you are dead wrong on the 6 wires thing. That part I do remember.

Trader is dead wrong about a lot.