On 08/07/2018 07:47 PM, wrote:

[snip]

If you have 3 conductors (one of which is neutral), how would you
determine if the others had the same phase or different phases? No
cheating please.

There are 2 possibilities right away.
That is where you actually need to understand the distribution systems
used in the US.
I would need to determine what kind of system I was looking at. Simply
poking around with a meter or even a scope, is not going to give you
that answer unless you understand that.

I did actually leave out something, that the 2 non-grounded conductors
carry the same voltage at the same frequency.

That and a voltmeter is all you need. There's no need to bring in
extraneous information, like power distribution systems.

If the 2 conductors carry the same phase, the voltage changes (AC) are
in step, so at any time they have the same voltage on them. The
difference is 0V and that is what you measure. No need for any of that
complex stuff, like where those conductors came from. It works the same
if you have 2 synchronized electronic inverters with a DC supply.

BTW, 240V is NOT the same as 0V.

Also, I remember someone talking about synchronizing generators by
putting a light bulb between the outputs. Same phase: no light.

[snip]

--
Mark Lloyd
http://notstupid.us/

"If a man would follow, today, the teachings of the Old Testament, he
would be a criminal. If he would follow strictly the teachings of the
New, he would be insane." -- Robert G. Ingersoll