On 11/18/2013 9:08 AM, 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.

BUT: why would center tap be anywhere near neutral?

The secondary centertap is the "neutral" because it carries the
imballance of the current in the secondary hot wires - the ends of the
240V winding. That is a common definition of a "neutral".

The secondary has no relationship to the primary, it is isolated from
the primary.

The secondary relationship to earth depends on how the secondary is
connected. The "neutral" (centertap) is earthed at the transformer. The
neutral is then also earthed at the building. That limits the maximum
voltage in the building with respect to the earth.



Choose leg to leg: does the same problem exist?

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

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