On Dec 30, 2:30*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

Power Factor is related to inductive or capacitive loads. It is best
seen if you take it to an extreme with a load that is 100 capacitive.
Lets say you put a capacitor across the line and measure the current
at 10 amps. This current is not doing any work and is returned to the
circuit. It doesnt show up on your electric bill and is not read by
your power meter. This is only more or less true. The more or less
part come in because the cables that carry the current to and from
this capacior are not perfect conductors, they are resistive. The
increased current caused by the capacitor increases loss on the lines.
These losses turn into heat which you will have to pay for. For
resisdential use it wont be very much for industrial use it could be
quite a bit. PoCos also have extra charges for places who have a
highly reactive load because it causes greater losses on the PoCo's
power lines. Their are lots of myths that you can add capacitors or
inductors to reduce your eelctric bill and even get free electricity.
Neither are practical for residetial users. The free electricity myth
isnt true for any type of user.

Jimmie

In ,
JIMMIE typed:
On Dec 30, 2:30 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

Power Factor is related to inductive or capacitive loads. It is best
seen if you take it to an extreme with a load that is 100 capacitive.
Lets say you put a capacitor across the line and measure the current
at 10 amps. This current is not doing any work and is returned to the
circuit. It doesnt show up on your electric bill and is not read by
your power meter. This is only more or less true. The more or less
part come in because the cables that carry the current to and from
this capacior are not perfect conductors, they are resistive. The
increased current caused by the capacitor increases loss on the lines.
These losses turn into heat which you will have to pay for. For
resisdential use it wont be very much for industrial use it could be
quite a bit. PoCos also have extra charges for places who have a
highly reactive load because it causes greater losses on the PoCo's
power lines. Their are lots of myths that you can add capacitors or
inductors to reduce your eelctric bill and even get free electricity.
Neither are practical for residetial users. The free electricity myth
isnt true for any type of user.

Jimmie

Eggzactly. Well put too.

--
--
Cats land on their feet.
but Toast lands PB side down;
A cat glued to some jelly toast will
hover in quantum indecision forever.