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PICList Thread
'[OT]Power Factor Correction'
1999\11\19@225034 by Alan Aldaba

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face
Hi Everyone,

       I've seen on TV advertisement, a device which promises to bring down
electricity consumption. Interestingly, they show a test, wherein they
plug the device in one of the outlets  where other appliances such as
refs, TV's, aircons, motors and the likes are also plugged in. The
ammeter shows significant drops in readings. Are these devices, safe to
use together with our appliances, do you recommend these kind of devices
?
       I understand that these devices has something to do with power factor
correction, can you point some resources where i can learn more.
Is a PIC based power factor corrector feasible,can you give me hints on
how to go about it. If it is ok, maybe i'll push thru with it one of
these days....

All The Best,

               Alan

1999\11\19@230944 by hgraf

picon face
>         I've seen on TV advertisement, a device which promises to
> bring down
> electricity consumption. Interestingly, they show a test, wherein they
> plug the device in one of the outlets  where other appliances such as
> refs, TV's, aircons, motors and the likes are also plugged in. The
> ammeter shows significant drops in readings. Are these devices, safe to
> use together with our appliances, do you recommend these kind of devices
> ?
>         I understand that these devices has something to do with
> power factor
> correction, can you point some resources where i can learn more.
> Is a PIC based power factor corrector feasible,can you give me hints on
> how to go about it. If it is ok, maybe i'll push thru with it one of
> these days....

   Chances are it is a very simple device, all it does is try to match the
amount of capacitance or inductance on the system with the opposite, which
eliminates the amount of complex power consumed. When you saw this
demonstration which ammeter did they show, a hand held one? Did they show
the actually power meter that the electrical company reads slow down? I
doubt it since I believe all meters ignore the effects of this sort of
thing. I don't believe it would damage anything, but I don't think it would
reduce the amount of power the power company charges you for using, I might
be wrong though. TTYL

1999\11\19@235629 by Mark Willis

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Herbert Graf wrote:
{Quote hidden}

My understanding's that the power company doesn't charge you for
REACTIVE loading, just real power you use, for regular consumers.
(Industrial users can get a discount for presenting a less inductive
load, but that's an entirely different bushel of worms!)  I haven't
heard a whole lot of power experts comment positively on those.

 Mark

--
I do small package shipping for small businesses, world-wide.

1999\11\20@014556 by hgraf

picon face
> > the actually power meter that the electrical company reads slow down? I
> > doubt it since I believe all meters ignore the effects of this sort of
> > thing. I don't believe it would damage anything, but I don't
> think it would
> > reduce the amount of power the power company charges you for
> using, I might
> > be wrong though. TTYL
>
> My understanding's that the power company doesn't charge you for
> REACTIVE loading, just real power you use, for regular consumers.
> (Industrial users can get a discount for presenting a less inductive
> load, but that's an entirely different bushel of worms!)  I haven't
> heard a whole lot of power experts comment positively on those.

       That's what I believe as well, can anybody confirm, I'd be interested in
knowing if these are just the same devices I heard of before or if they are
something new. TTYL

1999\11\20@042049 by p.cousens

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Herbert Graf wrote:
>
> > > the actually power meter that the electrical company reads slow down? I
> > > doubt it since I believe all meters ignore the effects of this sort of
> > > thing. I don't believe it would damage anything, but I don't
> > think it would
> > > reduce the amount of power the power company charges you for
> > using, I might
> > > be wrong though. TTYL
> >
> > My understanding's that the power company doesn't charge you for
> > REACTIVE loading, just real power you use, for regular consumers.
> > (Industrial users can get a discount for presenting a less inductive
> > load, but that's an entirely different bushel of worms!)  I haven't
> > heard a whole lot of power experts comment positively on those.
>
>         That's what I believe as well, can anybody confirm, I'd be interested
in
> knowing if these are just the same devices I heard of before or if they are
> something new. TTYL

The way I see it is that with a inductive or capacitive load the current
peak is not
at the voltage peak

So as the consumer meter only measures current, you are getting less
power for your
money
ie: with a resistive load  10Amps x 120Volts = 1.2KW
   with a reactive  load  10Amps x 100Volts = 1KW

I don't think it takes much to shift the peak current from 120V to 100V
in an industrial
enviroment but for a home the savings could be small

I would say that savings could me made by putting a cap across the
fridge motor though. !
IF YOU KNOW WHAT YOUR DOING
--
Peter Cousens
email: spam_OUTp.cousensTakeThisOuTspamcwcom.net  or  .....p.cousensKILLspamspam@spam@virgin.net
smail: 48, Yarmouth Cresent, London, N179PQ, England.

1999\11\20@051129 by Robert A. LaBudde

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<x-flowed>At 11:49 AM 11/20/99 +0800, Alan wrote:
>         I've seen on TV advertisement, a device which promises to bring down
>electricity consumption. Interestingly, they show a test, wherein they
>plug the device in one of the outlets  where other appliances such as
>refs, TV's, aircons, motors and the likes are also plugged in. The
>ammeter shows significant drops in readings. Are these devices, safe to
>use together with our appliances, do you recommend these kind of devices
>?
>         I understand that these devices has something to do with power factor
>correction, can you point some resources where i can learn more.
>Is a PIC based power factor corrector feasible,can you give me hints on
>how to go about it. If it is ok, maybe i'll push thru with it one of
>these days....

These devices work for motors which have variable loads and idle a fair
amount of the time. The original circuit was patented by NASA and is used
on industrial motors to reduce cost. I've got one 'Watt Wizard' attached to
my refrigerator.

I suggest you search for the NASA patent. As I remember, the device
controls the phase angle of the power to minimize power for a given torque.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ralspamKILLspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

</x-flowed>

1999\11\20@120054 by Charles Linquist

picon face
In many cases, the extra circuits everyone is describing are not Power
Factor Controllers at all.

I have one of the devices, and (wonder of wonders) it uses a PIC 16C54 !!!!

Most appliances need more power to get started than to run, and most
induction motors
(even with capacitor start) have higher running torque than starting torque.
For that reason, motors must be oversized to handle the increased load
during start.

These "oversized" motors waste energy during running.  The little add-on
controllers allow for
full voltage during startup, and back it down to 85 - 95 during normal
operation.  This
saves a significant amount of electricity. Of course, since we are dealing
with AC, reducing
the RMS voltage usually involves reducing the duty cycle.  This is done with
TRIACs.

Some intelligence in the device is needed, because if the appliance requires
more power,
the controller must respond by providing 100% duty cycle.  This load is
determined by the
relationship between voltage and current.  If both are in phase (zero
degrees phase shift),
the motor is heavily loaded. As the motor's load drops off, the phase angle
between voltage
and current increases, and the controller reduces the motor voltage until
the phase angle is again
close to zero.  The need for such intelligence is the reason a PIC is
employed.

The savings are roughly proportional to the amount of voltage reduction.  I
have such
a controller on my refrigerator, and it backs the voltage down to about 90
volts during normal
operation.  It is interesting to note that when I have the door open, and
the motor starts,
the refrigerator door light gets brighter, and five or ten seconds later ,
the light gets dimmer.

Also note:  The electrical power meters on your house do NOT just measure
current!  They
actually have voltage and current coils, and do a "magnetic multiply",
thereby showing
actual RMS watts (vector voltage X vector current) used.



{Original Message removed}

1999\11\20@153546 by paulb

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Mark Willis wrote:

> My understanding's that the power company doesn't charge you for
> REACTIVE loading, just real power you use, for regular consumers.

 The story goes ... that the electricity supplier doesn't like you to
have a capacitive ("leading") phase angle because the electricity meter
isn't calibrated for this condition and will under-read, even run
backward if the phase angle is severely capacitive!

 Obviously this applies only to the traditional motor-based power
meters and not electronic ones (when/ if they are deployed).

 I find it quite plausible since these are obviously based on a motor
whose directional torque is generated by a phase-shifting mechanism.
The big visible aluminIum disc is not the motor but the "drag" disc
between two large magnets.
--
 Cheers,
       Paul B.

1999\11\20@154212 by Robert M. McClure

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At 09:22 AM 11/20/99 +0000, Peter Cousens wrote:
...
>So as the consumer meter only measures current, you are getting less
>power for your money
...
In the US, most consumer meters measure only actual power, not current
and not voltage.  This has been the tradition for nearly 100 years.
Don't know about the rest of the world.  Improving the power factor
therefore, will not save you any significant amount of money.  The only
savings is in the additional I square loss in the copper on your side
of the meter.  Hardly significant.

Bob McClure

1999\11\20@161203 by p.cousens

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Paul B. Webster VK2BZC wrote:
snip
> The big visible aluminIum disc is not the motor but the "drag" disc
> between two large magnets.

There is no other motor, the disk is the motor.

--
Peter Cousens
email: .....p.cousensKILLspamspam.....cwcom.net  or  EraseMEp.cousensspam_OUTspamTakeThisOuTvirgin.net
smail: 48, Yarmouth Cresent, London, N179PQ, England.

1999\11\20@170943 by paulb

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Peter Cousens wrote:

> There is no other motor, the disk is the motor.

 OK, I'll go with that.
www.usbr.gov/power/data/fist/fist3~10/3~10_3.htm
--
 Cheers,
       Paul B.

1999\11\20@173430 by wilf

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This has been most interesting watching this OT. Could our American friends
confirm that the electricity supply meters (domestic)as stated by Bob
McClure measure true power (KW) in the UK our meters only measure KVA.

As to the devices, I have recently seen them advertised for use on domestic
fridges. These devices are fitted in a replacement mains connector, 13amp
plug in UK. I wonder how the electronic circuit that makes up the
temperature control manages with this reduced voltage, I hope the 240/5 or
110/5 volt conversion is up to it eg not a Tx

Wilf Melling

{Original Message removed}

1999\11\20@184527 by Wagner Lipnharski

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"Paul B. Webster VK2BZC" wrote:

>   The story goes ... that the electricity supplier doesn't like you to
> have a capacitive ("leading") phase angle because the electricity meter
> isn't calibrated for this condition and will under-read, even run
> backward if the phase angle is severely capacitive!

Paul, what you say, is that if I create a device and install it between
the electric meter and all my house wiring, and by any way this device
cause a strong shift in current angle, say 90¡ to Voltage, reflected to
the meter, and correct it back to my house wiring, I would be paying
almost zero of power consume?  But according to what you said, meters
are calibrated differently, as if they would be expecting some incorrect
power factors, so probably that "free" angle should be not exactly 90¡.  

Question:  Why should a meter take current *AND* voltage to calculate my
house's power consume?  Reading just current should be enough, since
voltage is a known element and by this way they can avoid problems with
power factor messing with their measurement...

1999\11\21@020132 by Steve Landas

picon face
I don't know much about how the power company changes for power but I do know
a little about PFC. Power Factor Correction is also used to reduce the
harmonic noise devices put on a power line. For example, a simple bridge
rectifier and filter cap to convert ac to dc creates a lot of harmonic
distortion. This is because the cap can't draw current until the rectified
voltage is > than the DC output voltage. Therefore the capacitor must draw
larger amounts of current over shorter periods of time. An AC outlet may be
able to run 4,100 watt power factor corrected devices but only 2,100 watt non
power factor corrected products. This is because the PFC. devices peak
current draw will be nearly equal to its average current draw. But the peak
current on the non PFC. device may be >> than its average draw.

Just some food for thought

Steve

1999\11\21@072003 by paulb

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Wagner Lipnharski wrote:

> Paul, what you say, is that if I create a device and install it
> between the electric meter and all my house wiring, and by any way
> this device cause a strong shift in current angle, say 90¡ to Voltage,
> reflected to the meter, and correct it back to my house wiring, I
> would be paying almost zero of power consume?

 The suggestion as I heard it was that most appliances are either
pure resistive or inductive.  Domestic fluorescent lamps rarely have
correction capacitors (just another part that sometimes goes "bang" and
emits pungent smoke).

 It is therefore argued that the meters are compensated for inductive
loads but not a strongly capacitive load and indeed have a design
limitation there (related to the motor requiring a "lag" circuit to make
it rotate).

 No alteration to fixed wiring is involved.  The supposed "cheat"
device is merely a (switched) gang of induction motor run capacitors
plugged into any power outlet to over-compensate the whole system (which
depends on what you are doing already) so that at light loads, the meter
runs backward.

 Such is the claim, I have not tried it.  It is pertinent to note that
capacitors are somewhat unfriendly devices to switch into circuit (and
inductors are correspondingly unfriendly devices to switch *out* of
circuit too!) and should have bleeder resistors.  Imaging pulling the
plug out...

> so probably that "free" angle should be not exactly 90¡.

 It may be as little as 45¡ capacitive.

> Question:  Why should a meter take current *AND* voltage to calculate
> my house's power consume?

 Because they are required to be *fair*.

>  Reading just current should be enough, since voltage is a known
> element

 No way!  Surely you realise that the line voltage is anything *but* a
known constant.  20% variation is quite common (100 to 120V on a 110V
line).  The meter must accurately measure power to within a few percent,
(under *reasonable* loading conditions - and there is the trick) and
unless the contract states penalties for reactive loading (see the
website I gave for specific metering of reactive power!), this most
certainly means real and not imaginary power!

> and by this way they can avoid problems with power factor messing with
> their measurement...

 Indeed it is necessary to measure the voltage and current to determine
the in-phase product for this very reason - to *avoid* power factor
"messing with" the true power measurement.
--
 Cheers,
       Paul B.

1999\11\21@114139 by Robert M. McClure
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At 10:21 PM 11/20/99 -0000, Wilf Melling wrote:
>This has been most interesting watching this OT. Could our American friends
>confirm that the electricity supply meters (domestic)as stated by Bob
>McClure measure true power (KW) in the UK our meters only measure KVA.
>
Quoting from the 12th Edition of the Standard Handbook for Electrical
Engineers (Fink and Beatty, McGraw-Hill) p 3-31 et seq

81. General  The subject of metering electric power and energy is
extensively covered in the American National Standard C12, "Code for
Electricity Metering," American National Standards Institute.  It covers
definitions, circuit theory, performance standards for new meters, test
methods, and installation standards for watthour meters, demand meters,
pulse recorders, instrument transformers, and auxiliary devices.  Further
detailed information may be found in the Handbook for Electric Metermen,
Edison Electric Institute.

...
83. Energy is measured in watthours (or kilowatt hours) by means of a
watthour meter.  A watthour meter is a motor mechanism in which a rotor
element revolves at a speed proportional to power flow and drives a
registering device on which energy consumption is intergated.  Meters for
continuous current are usually of the mercury-motor type, whereas those
for alternating current utilize the principle of the induction motor.

...

This extensive section includes information on adjusting meters to insure
that *watts* and *not kva* are measured.  This includes testing the meters
at various power factors.  This concludes with acceptance accuracy limits
from the Code for Electricity Metering, ANSI C12-1975, which prescribes
that accuracy must be within 2% at a power-factor lag of .5.

KVA meters are occasionally used, but primarily for some specific industrial
applications that operate at extreme power factors.  I have never seen or
heard of one in use in residences.

And yes, the previous remark to the effect that the aluminum disk is indeed
the motor is correct, and has been since early in this century.

If I might be permitted an anecdote.  One of my professors of electrical
engineering (circa 1954) started his career after receiving his EE degree
in the midst of the depression in the 1930's as an ordinary lineman.  (It
was the only job he could get.)  He was assigned to find out why this old
farmer had electricity usage much lower than could be inspected.  The had
his meter tested and it proved accurate.  Then one day as he was starting
at the meter on the wall, he noticed an ant crawling inside.  Upon close
inspection a tiny hole was discoved drilled through the wall behind the
meter and into the meter.  It seems that the farmer would insert a wire
through the hole and stop the rotation of the rotor when he didn't want
his electricity usage recorded.

Bob McClure

1999\11\21@114144 by Robert M. McClure

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At 06:43 PM 11/20/99 -0500, Wagner Lipnharski wrote:
>"Paul B. Webster VK2BZC" wrote:
>
>>   The story goes ... that the electricity supplier doesn't like you to
>> have a capacitive ("leading") phase angle because the electricity meter
>> isn't calibrated for this condition and will under-read, even run
>> backward if the phase angle is severely capacitive!
>

Not quite, you can't get the power factor to less than zero.  The only
way to get the meter to run backward is to send power back to the line.


>Paul, what you say, is that if I create a device and install it between
>the electric meter and all my house wiring, and by any way this device
>cause a strong shift in current angle, say 90¡ to Voltage, reflected to
>the meter, and correct it back to my house wiring, I would be paying
>almost zero of power consume?  But according to what you said, meters
>are calibrated differently, as if they would be expecting some incorrect
>power factors, so probably that "free" angle should be not exactly 90¡.  
>

Not quite the case.  A watt-hour meter measures (if calibrated correctly)
the power actually consumed regarless of currents of other phase angles.
Hence, no free power.

>Question:  Why should a meter take current *AND* voltage to calculate my
>house's power consume?  Reading just current should be enough, since
>voltage is a known element and by this way they can avoid problems with
>power factor messing with their measurement...
>

The reason that both voltage and current are required is that 1) voltage
is *not* constant (it can vary from 110-125 volts and remain within the
standard limits), and 2) the phase angle between the voltage and current
must be known.

Bob McClure

1999\11\21@153557 by Tom Handley

picon face
  Bob, PF controllers can and will save energy in the USA using the
`ancient' meters installed outside our houses. Just last week, EDTN
had a pointer to why many engineers will have to deal with this. It's
not just for refrigerators anymore. It's about to be a standard...
Forget about how the power company looks at power and consider the
actual energy consumption from a switching power supply or an
appliance with motors.

  I'm not really responding to you directly but you happen to be in
my `sights' ;-) Normally, I would provide links but I've been up all
night, trying to catch up here...

  - Tom

At 11:17 AM 11/20/99 -0700, Robert M. McClure wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

1999\11\22@000938 by Agnes en Henk Tobbe

flavicon
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>Bob McClure wrote:  It seems that the farmer would insert a wire
>through the hole and stop the rotation of the rotor when he didn't want
>his electricity usage recorded.
>
NOT only US farmers were that clever, but a dutchman in the "thirties" had
the same idea... This resulted in a still famous Dutch Supreme Court
decision (as my law books are still packed because of my recent move to
Australia, I am afraid I can not give the official reference). At the time
the crime of  "theft" on the Criminal Code was defined as: " taking  a good
or goods belonging wholly or partly to others, without their consent and
with the intent of keeping it as your own good".  Under dutch criminal law
only crimes as defined as such on the statute book are punishable. The
universal principle being that one can only be punished for an act of which
it is made clear in advance that it is  a punishable offence. (One of the
problems of prosecuting war criminals after WW II as war crimes had not been
defined as such at the time).
Well the "hole driller" pleaded that electricity  - one cannot "take it
away" as it is - was not a "good" so the taking of electricity would not be
punishable. This plea was accepted in the lower courts, but the dutch
Supreme Court ("Hoge Raad")  held that is was  and that theft of electricity
was theft of a good as indicated in the relevant par. of the criminal code.
After that our clever dutchman -  for a while  - was able to enjoy some more
free electricity at the cost of the dutch taxpayer....
Henk Tobbe -
VK2GWK - HENK

Home page: http://www.users.bigpond.com/tobbe/index.htm

1999\11\22@062920 by ruben

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Hello,

One thought on the subject of reducing power cost.

If the meter is based on a motor it takes some time for it to
increase its speed when power is increased. During this time the
meter registers less power than actually is consumed. Of course it
also takes time for the motor to decrease its speed when power is
reduced so in normal circumstances these effects would zero out each
other. But what if the motor isn't allowed to reach its full speed (for
the power used) by pulsing the power (current in this case) outtake. Say I
take out 30 Amps for one complete cycle every 30th cycle instead of taking
out 1 Amp continuously. Will this reduce the power registered by the
meter?

In other words, how many cycles does it take for the motor to reach
its full speed when power is increased.

Of course the the higher power outtake has to be stored somehow
possibly in capacitors or batteries after a AC to DC converter and
the be re converted and regulated by a DC to AC converter. With
conversion losses, maybe I would end up using more power after all:)

Oh well, just a thought...

{Quote hidden}

==============================
Ruben Jvnsson
AB Liros Elektronik
Box 9124, 200 39 Malmv, Sweden
TEL INT +4640 142078
FAX INT +4640 947388
rubenspamspam_OUT2.sbbs.se
==============================

1999\11\22@110238 by Terry A. Steen

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Get a GRIP guys!

Power meters (real ones that is) measure POWER, not VARs (either type). You
are not 'tricking' the power company, you are using less power.

The circuits are simple triac circuits that hold the device off for the
first 0-45 degrees of current. Any power (the positive componant of V*I)
that this current would have used is gone. MOST of the power used is taken
from more than 25 degrees to 25 degrees after the crest. You ARE using less
power.

BTW: These same devices are also marketed to 'quiet' motors. They work by
letting the motor coast to its next quadrant instead of putting a field on
it and forcing it there. So, alot of the 'rattle' in the motor is gone by
getting rid of the cross-over time.

BTW2: YES! Power companys like inductive loads and HATE capacative loads.
Easy reason--- they have capacitor banks that compensate for inductors, but
do not have inductor banks to compensate for capacative loads. When the
loads become too inductive, cap-banks lock in, and lock out when the
induction is gone. They like having a simple way to effect phase.

That was fun!

TAS

At 11:49 AM 11/20/99 +0800, Alan Aldaba wrote:
{Quote hidden}

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332 McLaws Circle, Ste 111         757-258-8800 (Voice)
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1999\11\22@120637 by Morgan Olsson

picon face
Terry A. Steen. Wrote:

-snip-

>The circuits are simple triac circuits that hold the device off for the
>first 0-45 degrees of current. Any power (the positive componant of V*I)
>that this current would have used is gone. MOST of the power used is taken
>from more than 25 degrees to 25 degrees after the crest. You ARE using less
>power.

Just wondering...
Instead of softly pushig it, you kick it hard shorter time...  feels like the lo
sses wuld increase as the I2R losses are much larger.

I hav never seen any independant evalutaion of the idea neither in theory nor in
practice.  Anybody?

Instead, adding a transformer to lower the voltage suitable would be better... b
ut also the transformer have losses... and adds more inductance...

>BTW2: YES! Power companys like inductive loads and HATE capacative loads.

NO!  I was once practising i a local power company.
There was an automatic central capacitor bank.
They have not installed any inductor banks simply because there is no risk at al
l that the total sumn of customer power would be capacitive.  Also, a large indu
ctor battery would have more losses than a capacitor battery.
In elder days when capacitors this large was expensive to switch in/out, they us
ed large synchronous AC motors, and by overfeeding the rotor magnetization they
woud get a "negative" angle like a capacitor, variable by applied DC rotor curre
nt.
Also all those line voltage transformers are inductive enough...
The power company tries to get towards zero phase angle to get the lowest buy pr
ice for the electricity, as the losses in the lines from power plant then decrea
ses.
Also of course they like us customers to have close to zero power to minimize I2
R losses in thei distribution net and transformers, and also needing less big ca
pacitor battery.  But they only measure and demand the angle from large customer
s.

/Morgan

1999\11\22@123026 by Terry A. Steen

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face
way cool NON-PIC forum.

The entire rim of the great lakes and the area surronding New York City
have capacitor banks. This is because (don't recall the year) a power
failure in a sub station caused a reroute of power. They found an extreme
phase shift on the lines (I want to say .7-.8 power factor). A great deal
was air conditioning systems and motors because there was a major heatwave
underway (think it was '85). A cascade of substation failures killed power
from New York to Canada.

The solution was capacitor banks put in place to absorb the ind vars. All
they want to do is lower the line current of the power carriers. They could
make the power, but much of it was lost on the road to the user.

In either event, yeah, free power is a nice idea... but nore effective use
of the power you are using is THE BEST>>>>>>

and thus the MICRO-controller

TAS


At 05:55 PM 11/22/99 +0100, Morgan Olsson wrote:
{Quote hidden}

the losses wuld increase as the I2R losses are much larger.
>
>I hav never seen any independant evalutaion of the idea neither in theory
nor in practice.  Anybody?
>
>Instead, adding a transformer to lower the voltage suitable would be
better... but also the transformer have losses... and adds more inductance...
>
>>BTW2: YES! Power companys like inductive loads and HATE capacative loads.
>
>NO!  I was once practising i a local power company.
>There was an automatic central capacitor bank.
>They have not installed any inductor banks simply because there is no risk
at all that the total sumn of customer power would be capacitive.  Also, a
large inductor battery would have more losses than a capacitor battery.
>In elder days when capacitors this large was expensive to switch in/out,
they used large synchronous AC motors, and by overfeeding the rotor
magnetization they woud get a "negative" angle like a capacitor, variable
by applied DC rotor current.
>Also all those line voltage transformers are inductive enough...
>The power company tries to get towards zero phase angle to get the lowest
buy price for the electricity, as the losses in the lines from power plant
then decreases.
>Also of course they like us customers to have close to zero power to
minimize I2R losses in thei distribution net and transformers, and also
needing less big capacitor battery.  But they only measure and demand the
angle from large customers.
>
>/Morgan
>
>
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1999\11\22@220512 by Eric Smith

flavicon
face
Wagner Lipnharski <RemoveMEwagnerTakeThisOuTspamUSTR.NET> wrote:
> Question:  Why should a meter take current *AND* voltage to calculate my
> house's power consume?  Reading just current should be enough, since
> voltage is a known element and by this way they can avoid problems with
> power factor messing with their measurement...

No.  The power company wants you to look like a resistive load.  Let's
say your load is a perfect 1 Ohm resistor, and you put it across your
117V RMS  power line.  It doesn't draw 117A all the time; it draws 117A RMS.
When the line voltage is at 10V, the load draws 10A.

If the load were to draw 117A continuously, you would be using a lot more
power.

Similarly, if the meter only measured how much current your load draws,
without regard to the simultaneous voltage, it could not accurately
measure the power consumption.

1999\11\22@220541 by Eric Smith

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Steve Landas <spamBeGoneSLandasspamBeGonespamAOL.COM> wrote:
> This is because the PFC. devices peak
> current draw will be nearly equal to its average current draw. But the peak
> current on the non PFC. device may be >> than its average draw.

Shouldn't the peak current on the PFC device be about 1.4 times the average
(RMS) current?

1999\11\22@224725 by Wagner Lipnharski

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face
It made me think something else.  If the two coils at the meter are
measuring Voltage and Current, and it is 60Hz AC, it means that the
instant power for a constant load is also a senoidal curve.  It doesn't
mean that the disk is following that frequency, registering exactly the
instantaneous power consumed, and it works by inertia, so the disk in
real is doing the RMS by itself.

I was talking to a friend who works in a plant that produces power
meters in northeast of Brazil. He told me that the counting mechanism
counts forward doesn't matter if the disk is running forward or
backward. So, differently from what somebody said, if you *generate*
power and send to the external lines, your meter will still accounting
it as "consumed power"... :)

He also said that the meters are aligned to work with a power factor >
.85 and that a peak of power during 1/60 of a second (one whole senoid)
could cause a misread, in favor or against you... :)  He also said that,
yes, if you could change strongly the power factor to a very low value,
and then convert it to a useful power, the meter will account less power
than what was really consumed at your residential meter.  He said only
electronic industrial meters analyze power factor to make correct
accounting, even with power factors less than 0.5

He will post me more information about it.

Wagner.

Eric Smith wrote:
{Quote hidden}

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