Jeffrey Angus wrote:

On 1/22/2011 7:27 AM, PeterD wrote:

Well, if you want to be correct, the house power is split phase, and
not two phase. I suppose there is an arguement that it is two phase,
but say that to a power engineer and you'll get the old raised
eyebrows response!


Ding! We have a winner.

Thank you peter.

Jeff

having a CT in a winding gives you 2 phases, 180 apart..

Calling it split phase is just a method of doing it.

Lets look at it this way..

Take a control xfomer..

If I was to wire the secondary as

X1, X2+X3, X4;

X2 and X3 being the CT, I now have a source that has 2 secondaries
(2 windings) that can give me 180 degree shift via the CT. This gives
me 2 phases..Why? because they are not in phase with each other.. It
does not matter if they are only 1 degree off from each other.. They
would be two difference phases, because we are using the CT as the
common point. Same as, if you were to use the STAR Center of a WYE
transformer as the common point, this would give you 3 phases which
we all know are 120 degrees different from each one. The analogy isn't
any different if you had the pole pig which is just a single winding
with a CT in it on the secondary side for your common. Other wise known
as a split phase because can treat that as a single phase to get the
full voltage or split phase to get half voltage with 180 shifts.(2 phases)


Now, take that same xformer I have above there and....

X2, X1+X3, X4;

What do you get? You get two different power points sharing a CT but
in phase with each other. And yes, I've seen this done before to avoid
over voltage through grounds if the neutral was ever lifted for some
reason. This basically is only one phase and does not allow you to
use them for double voltage. In fact, you'll get no voltage between X2
and X4.


Oh well.

Jamie