On Monday, September 9, 2019 at 5:33:54 PM UTC-4, Clare Snyder wrote:
On Mon, 09 Sep 2019 16:46:38 GMT, (Scott Lurndal)
wrote:

trader_4 writes:
On Sunday, September 8, 2019 at 7:12:34 PM UTC-4, Ralph Mowery wrote:
In article ,
says...

Do you have single-phase or two-phase electric service?
No such thing as 2 phase



There is (was). What is split phase in most of the US is mistakenly
called 2 phase by some. However there really is 2 phase.
I hop ewe don't have to go through the same old 400 postings about this.

If you had that hope, why did you take the troll bait?

You start off with the wrong assumption that because one particular system
of two phase was called two phase, that means that defines what two phase
means. To do this right, you first need to define what an N phase power
service would look like. Hint: It's not limited to 90 degrees phase
difference. I have defined it in the past, no one else has.

So, here are your questions. Let's take your second example of what you
say was the old two phase power, ie 90 deg phase difference, three wires with
a common return. I changed the phase difference to 70 deg by rotating
one of the windings on the generator. Are there
still two phases there? Now I change it to 179 deg, are there still
two phases there? I change it to 181, are there still two phases there?
I change it to 180 deg, are there still two phases
there? And how is the latter any electrically different than the
3 wire 240/120V service going into a home? Describe how I could tell
from the panel in your house which of the two I had, how they are
electrically different, how they behave differently?

This is based on semantics without definitions and reliance on what
something was historically, not electrical engineering. Would I call
240/120V, two phase? No, because it's not commonly referred to as that,
but that does not change the fact as to what's actually there, you
have two 120V sources that are 180 deg out of phase with each other.

Are they 180 degrees? or 120 degrees. Most AC is distributed as three-phase
power. Each neighborhood here gets one of the three phases from the
the power yard where the incoming three-phase 115kVAC is transformed to
21kVAC or 12kVAC (depending on age of neighborhood) for distribution. That means the
two hot conductors at the service entrance are drived from two of the three
distribution phases, which would make them 120 degrees apart. That phase is split
using a grounded conductor (AKA Neutral) into two 120VAC circuits.
No, most residential power is derived from a single phase of the 3
phase distribution system. The primary of the branch transformer is
accross ONE phase of the ncoming power,and the secondary is center
tapped - providing a "split" phase where each side of the service is
180 degrees out of phase with the other - making the voltage of the
two phases additive.

Oh my, while describing 240/120V service, Clare just said the voltage
of the "TWO PHASES" coming from the transformer are additive.
Bingo!






When derived from 2 phases of a 3 phase supply you get 120 and 208
(the sum of 120 degree out of phase)