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Tony Hwang Tony Hwang is offline
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Default How does the typical mains power connect in the USA anyway?

nestork wrote:
I've been kind of following this thread, and I can follow the notion
that in a perfectly balanced electrical load the voltage and current
sine waves would all cancel out when they met at the neutral wire and so
there wouldn't be any current or voltage in either the neutral or ground
wires.

But, in a real life situation, suppose I made a point of driving my CRT
style TV sets (capacitive loads) and CRT style computer monitors with
one power line coming into my house, and at the same time I used the
other 120 VAC power line to provide power to all of the electric motors
in my house, like the circulating pump on my hot water heating system,
the motor in my garage door opener and the compressor motor in my
fridge.

Now, according to ELI the ICE man, the current sine waves going through
the motors is going to lag behind the applied voltage sine wave, while
the current sine waves coming out of the CRT style TV sets and computer
monitors is going to precede the applied voltage sine wave. That would
mean that the current sine waves returning to the main panel along the
white wires would occur at different times, and therefore NOT cancel
each other out completely.

Now, I cannot fit it into my head that the voltage sine waves in the
neutral wires coming back from those two kinds of loads would cancel
each other completely in the neutral buss in the main panel, but not the
current sine waves. That would mean that you'd have some NET current
sine wave, and therefore current, without any driving voltage.

In order for there to be some NET current sine wave, there HAS TO BE
some net voltage sine wave in the white neutral buss in the main panel
where all the white wires meet to drive that current.

And I can't see why that net voltage sine wave wouldn't energize the
ground cable coming out of the main panel and cause current to flow
through that cable and into and out of the Good Earth.

What am I missing here?




Hmmm,
You are trying to say if I and V is out of phase by certain degree
there will be a current flow which is wasteful. That current does not
do any work. That is why in big industrial site or buildings use power
factor correction device.