Power Factor Correction

Discussion in 'General Electronics Chat' started by 2rlp, Oct 18, 2007.

  1. 2rlp

    Thread Starter New Member

    Feb 27, 2007
    7
    0
    Hi,

    Is it possible to use Power Factor Correction in a residence having a 230 V single phase supply. Will power factor correction reduce the usage of power (in short will the amount in the bills be reduced). How does one do this power factor correction.

    Ron
     
  2. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    the billing depends on laws perhaps the power factor penalty only applies to large power consuming units.
    so i dont think it will help.
    power factor correction is mostly done by application of leading loads since most applications have a lagging P.F maybe u'll have to use a capacitor bank.
    but again i dont think it will help ur bills.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    You might see a tiny decrease in you bill if you are constantly running several horsepower worth of motors. Most residences would see no difference, as residentially used motors are both small and intermittent. Even if you've got big motors out in your shop, they still see only intermittent use, yes?
     
  4. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    Power meters only measure actual power used, not reactive power, so the short answer is that it will make no difference. Those selling devices which supposedly work on this principle are quacks. Reactive loads at home are usually negligible anyway.

    Now, in a quest for exactitude and nitpicking we could say that, as wires have a certain resistance, a reactive load causes heat dissipation in the wires and we are paying for this energy. True but if you calculate you will see that this energy lost is so insignificant that there is no way it would pay back to install anything which cost anything.

    Note that capacitors used to compensate for inductive loads need to be connected at the same point as the inductive load. You can't connect a capacitor somewhere to compensate for an inductive load elsewhere. In that case you are making things worse, not better.
     
  5. John Luciani

    Active Member

    Apr 3, 2007
    477
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    Also a lot of the big motors in shop tools have running capacitors (and startup capacitors)
    built-in.

    (* jcl *)
     
  6. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    induction motors always run on lagging pf
    synchronous may run at leading pf.
     
  7. wireaddict

    Senior Member

    Nov 1, 2006
    133
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    Watt-hour meters show actual power used because, with low power factor [PF] the current & voltage are out of phase from each other, they're not driving the meter wheel at maximum effriciency although the current through the meter is higher. If/when PF is at unity, voltage & current are in phase but the current demanded by inductive loads [& also switching power supplies & compact fluorescent lights (CFLs), etc.] becomes less. Therefore, although the current & voltage in the meter work together at unity PF, there's less current flowing through the meter so it still won't show higher power consumption.

    Although residential customers aren't penalized by power companies for low[er] PF it costs the utility companies more to generate & deliver the power because of the higher current required by devices with low PF which we all pay for. [Industrial customers are penalized in the US if their PF falls too low (below 80-85%).]

    One benefit to all users from having high PF is longer switch, relay, contactor & triac life since they'd encounter lower current & less voltage induced across them.
     
  8. GS3

    Senior Member

    Sep 21, 2007
    408
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    True but electromechanical meters are a vestige of the past as they are replaced by electronic meters.
     
  9. wireaddict

    Senior Member

    Nov 1, 2006
    133
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    Residential KW-H meters here in Michigan are still electro-mechanical. Not sure about larger commercial meters. Although I don't know for sure, I suspect that even the newest KW-H meters don't sense low PF & compensate for current & voltage being out of phase; if so, they wouldn't be true wattmeters. Industrial electric customers have VAR meters [probably at the utility companies' insistance] to determine PF but that doesn't solve the problem of generating plants needing to produce extra power to supply more current for residential & smaller commercial customers due to certain devices which have fairly low PF.
     
  10. techroomt

    Senior Member

    May 19, 2004
    198
    1
    aside from pf correction, some locality's utilize a "peak" detection meter, where you are charged not only on your kw/hr consumption, but also pro-rated with a peak multiplier. in this instance it is more economical, and good for other reasons, to attempt to balance the loads of your a and b lines as much as possible.
     
  11. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    In Spain the older ones still installed are electromechanical but they have been installing the electronic ones for quite some years now and you can find piles of old electromechanical meters dumped. Being a packrat (or recycler) I have recovered quite a few and have used them to measure power usage of things like A/C and have also given a few away to friends who found use for them. The new electronic units provide a lot of information which the older ones can't like peak usage etc. I suppose power factor is also one of the things it can report. But I do not believe the power company makes any use of all that information. They just charge for the energy used.

    I am surprised to hear new electromechanical meters are still being installed in the USA although I guess countries have spurts of development and then fall behind while other countries leapfrog ahead. I think it is in China where I have seen most new things in the last few years. There I saw for the first time electronic water meters connected to the internet and read remotely, LED traffic lights and other such things. Their GSM mobile network and service is way ahead of American mobile phones. Checking here I see the USA has 48 mobile phones per 100 people which is way behind most of the developed world. Most of Europe is above 83% with Italy up to 93% (Hong Kong 93 and Taiwan 106). China's mobile phone market is much larger than that of the U.S. and, contrary to what most people would believe, there is not one American phone company among the top ten, while there are two Chinese. I never cease to be amazed by the development I see in China every time I go there. But anyway, I went off on a tangent here.
     
  12. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    We still use electromechanical ones though they are slowly being replaced from past few years.
     
  13. saurabhkarnik

    Member

    Jun 22, 2008
    22
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    hey but have u ever noticed... the tubelight that we use is of 40W but it hardly gives op power of some 12W... so it would reduce the bill by great deal... and u r for getting the different motors that we use like fans compressors of AC and fridge... so i think even in residential areas it will help a lot
     
  14. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    To read the following link, one will have to skip past an advertisement, but I believe the information is worth the inconvenience: http://powerelectronics.com/power_management/motor_power_management/power-factor-correction-0507/

    Commercially available residential power conditioners cost around $600 for each 20A to be conditioned. I leave folk to count their own breakers and do their own math. In my current home, such an installation would require 42 centuries to pay for itself. :eek:
     
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