On 9/9/19 1:33 PM, Scott Lurndal wrote:
trader_4 writes:
On Monday, September 9, 2019 at 12:46:42 PM UTC-4, Scott Lurndal wrote:

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.

The 240/120V service into a house is two 120V sources that are 180 deg
out of phase with each other. That's how you get 240V between the two
hots.

Not so. The 240v service to the house (from the pole pig if you have
one) is one phase of the three phase distribution.

The pole pig takes the 21KVAC (for example) and transforms it to 240VAC.

The grounded conductor starts at the dist transformer, pole pig or service
entrance (a grounding rod (or collection thereof)).



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.

I see the typical residential transformer connected with one high
voltage lead going to one primary, not connected across two.

That's certainly not typical. We're fed from a 12kv primary (two
current carrying conductors) which is transformed to 240v for distribution to a
dozen or so homes. All underground from the nearest substation to
the distribution transformer and underground (direct burial) to the
service entrance.

There's no need to distribute the grounded conductor (AKA neutral),
by definition.

Aerial installations may include the grounded conductor for safety
reasons or to help support the cable(that's why there are three wires twisted to most standard
pole-pig based service entrances), but it will be grounded again at your service entrance anyway.

You've certainly noticed that there are two terminals on the pole
pig each for the primary and secondary - that's what provides you
with 240v; the grounded conductor isn't passed through the transformer
(but it may ground the pole pig can if it's metallic).

We have just two wires from the power company on the poles for
single phase power in my area.
It looks something like this:
https://www.hvacrschool.com/why-is-240v-called-single-phase/?print=print

I guess the power company's hot line is actually 13,000 volts
plus a bit .