B.B. wrote:

One question for now: What is power factor correction? I've found
the term several times today, but not the definition.


This is a nasty one. If you have an ideal power source providing a
sinusoidal voltage, then if you put that in series with a resistor,
current will flow, and the current waveform would be a sinewave. If
you then add a capacitor across the voltage source, current would
also flow through the capacitor. If you looked at the current waveform
across the resistor on the same scope trace as the current waveform
across the capacitor, they would look very similar (well, one would
be bigger than the other) but their peaks and valleys would have
shifted relative to each other. In fact, the current waveform through
the capacitor is "phase shifted" by +90° relative to the current
waveform through the resistor. Similarly, if you apply the sinusoidal
power to an inductor, its current waveform would also be a sinewave,
but it would be phase shifted by -90° relative to the waveform of
the current through the resistor.

OK, now here's the tricky part. Current flowing through a resistor
dissipates power, and it is called "real current". The term "real"
here is mathematical - it means that when you express the current
as a complex number it only has a real part and its imaginary component
is zero. However, current through either an ideal capacitor or an ideal
inductor does not dissipate power. This current is called "imaginary
current" for similar reasons.

OK so far?

Now let's move to a real-world situation. Electric AC motors are magnetic
machines. They have windings which "look" very much like an inductor. In
reality, any physical component has some resistance and almost certainly
some capacitance too, but if you compare the current waveform of an AC
motor with that of the current waveform into a resistor, you will see
that the motor's current is phase-shifted nearly -90° which is why it
is said to "look inductive". The way you can make the current flowing into
an AC motor look more like current flowing into a resistor is to add some
run capacitors across the motor leads. If you add about the right amount
of capacitors, then the power flowing will look like "real power".

The power company cares about this passionately. Why should you? Here's
the deal - if you are consuming 1 hp of power for your bench grinder, for
example, then current is flowing sufficient to provide 1 hp of real power.
But current is also flowing because the grinder motor looks inductive.
This current doesn't show up on your power bill but it surely will burn
up a wire or melt heaters in your motor control circuit. The way to minimize
the total (real + imaginary) current in your motor wiring is to add the
right amount of capacitance. This is called "power factor correction."

OK, I have never been a practicing electrical engineer -- my thing was
semiconductors and software. There are real EEs on this NG who will almost
certainly take exception to some of my wording, especially because it's
all off the top of my head, from memory, which memory all comes from college
which was more than 2 decades ago. However, I believe it's sufficient to
impart the essentials.

GWE