On Dec 30, 1:30*pm, David Nebenzahl wrote:
In a more-or-less recent thread up yonder (the one about LED lighting
that evolved into a discussion/argument about CFLs vs incandescents and
power factor, among other things), a technical term and concept (power
factor) was argued at length. I wonder how many folks actually were able
to follow those arguments.

Myself, I really didn't know just what this mysterious "power factor"
was. I did know that values lower than 1 were bad and caused power
distribution inefficiencies that resulted in real losses of energy and
money.

I now know what power factor is--sort of. The best explanation I ran
across on the web was this really simple one. Instead of taking the
mealy-mouthed Wikipedia approach of jumping in all cosines and formulae
phase angles and other fancy stuff and *then* explaining just what the
hell it *is*, this explanation is for the layperson:

* *Power factor in electricity is like efficiency. The best power factor
* *is 100%.

* *Consider a child on a swing. If you push them when they are going
* *backwards you will actually slow them down. In order to push with
* *maximum efficiency the motion of the swing and and your push must be
* *"in phase".

* *Similarly in electricity, voltage and current must be in phase for
* *optimum performance. Equipment such as motors, ballasts and variable
* *speed drives tends to move voltage and current out of phase with each
* *other.

[see athttp://www.carleton.ca/energy/powfac.htm]

Now that's the kind of explanation I like; simple and to the point. Of
course, the picky purist might object to the "best power factor is 100%"
thing (the best power factor is actually 1), but who cares? Now I
understand the concept.

So it turns out that PF is actually computed as the absolute cosine of
the phase angle, which also makes sense if one thinks about it. But I
still don't really have a handle on the meaning of this number. How low
does PF have to get before it's considered really bad? 0.8? 0.5? Don't
have much of a handle on that yet. (That's the problem with them
dimensionless numbers.)

I still don't know exactly how PF losses work in the real world, though
I can take an educated guess that they result mostly in heating in
transformers, transmission lines, etc.

--
I am a Canadian who was born and raised in The Netherlands. I live on
Planet Earth on a spot of land called Canada. We have noisy neighbours.

- harvested from Usenet

For a power factor of one, the voltage and current are in exact
agreement/phase for the peaks and nulls. If you apply a voltage to a
pure resistor, they are in phase and the power used is the product of
the voltage and current. If you apply a voltage to an inductor/motor/
transformer, the current lags behind the voltage somewhat and the
power into the device is not the product of the voltage times the
current, but the product of the voltage times the current times the
power factor. If you apply a voltage to a capacitor/condensor, the
current leads the voltage somewhat. Again, the actual power into the
device is the product of the voltage times the curent times the power
factor. If you have a very large inductance. the current will lag far
behind the voltage, and the actual power used in the device is small.
But, the power company still has to be able to provide the maximum
current to the device, but does not get much $$ since the power
atually consumed is much less. That is why the power companies do not
like inductive or capacitive loads. Compact fluorescent lights tend
to look like capacitive loads because they have a large inrush current
that leads the voltage and so altho the power companies will save some
power when these are adopted over a widespeard area, they will still
have to be able to provide the peak current that these lamps draw.
Fortunately, that peak curent is still well below what a resistive
incandescent light that puts out the same lumens uses.

Hope this helps.