On Monday, August 6, 2018 at 12:29:36 PM UTC-4, Single Phase wrote:
On 8/6/2018 11:04 AM, trader_4 wrote:
And that's why I've tried ten times now to lead you through a generator
example where I take what you say was two phase and morph it one
small step at a time into what is exactly the same as 240/120 service.
It's a perfect valid, very simple, electrical engineering analysis.
But you won't admit it because there are obviously two phases there.

A residential transformer secondary is one continuous conductor from end L1 to end L2.

Assuming a purely resistive load on the secondary and ignoring crossings where Volts=0,

at any point in time the current is either flowing from L1 towards L2 or from L2 towards L1.

In order for the transformer secondary to truly have 2-phases 180° apart, the current would have to be flowing from L1 towards L2 AND from L2 towards L1 at the same instant.

And that, my liberal friend, would be the mother of all parlor tricks.

That would be true only if the circuit did not have a center tap.
With the center tap it becomse TWO 120V voltage sources. Do you disagree
with that? If it does not become two 120V voltage sources, explain how
we get 120V with a load on just one side of the secondary.

With two voltage sources, it looks like two batteries stacked one on top of the
other. Do that. Put two 9V batteries one on top of the other with a
tap between them. You can no longer treat it as just current flowing
through both, from one end to the other. You have two conductors now
that are of OPPOSITE POLARITY or 180 deg phase difference in the AC
world. Put a load on just the upper half circuit and current flows
from the upper battery positive through the load and out the neutral back to
the upper battery negative That current is flowing out the neutral, yes?

OK, now instead put a load on the lower battery. Because it's of OPPOSITE polarity,
the current will flow from the lower battery positive through the neutral
through the load and out the
connection back to the negative side of the lower battery. It's current
flow in the OPPOSITE direction on the neutral. That is exactly what
happens with the transformer secondary. In the special case where the
loads happen to be balanced, the two currents in opposite directions
cancel each other out and you have zero neutral current.

The essence of the problem here is that you cannot have this service
working without TWO voltage sources, one has to be of the opposite polarity
of the other with respect to the neutral. Opposite polarity and a phase
difference of 180 are the same thing in an AC circuit.