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Energy Unassessed

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Confusing

The article is confusing. What do the various values of the power factor mean? Are they the same (just magnitude) for both sources and sinks? A diagram with at least -1, 0, and +1 would be helpful. How does leading and trailing play into this? Do only sinks have leading or trailing characteristics or do sources too? Does the utilization depend on matching them, or is +1 always desirable for sinks no matter what the value of the source?

If this isn't the right place for comments about the entry I apologise in advance. Please direct me to the proper place.

Power factor is confusing and is difficult to explain in simple terms. I don't fully understand it myself so the following should be treated with caution. When the PF is 1 it does not have a sign. If the PF is (say) 0.9, it can be "0.9 trailing" (-0.9) for a reactive load, or "0.9 leading" (+0.9) for a capacitative load. The question about sources is a good one but I don't know the answer. Biscuittin (talk) 09:35, 2 November 2009 (UTC)

Don't think so. Power factor meters in my experience say "lead" or "lag" and never "+" or "-" - this has been discussed quite a lot in connection with this page (see below under "Sign"). Where does the article get confusing to follow? --Wtshymanski (talk) 19:32, 2 November 2009 (UTC)

My mistake. I saw the + and - signs elsewhere on this page and assumed they referred to leading or trailing power factor. Biscuittin (talk) 19:55, 2 November 2009 (UTC)

energy returns to the source

I think that this sentence could do with a bit more explanation: "Since this stored energy returns to the source and is not available to do work at the load" - why is this exactly? --TimSmall 13:16, 1 September 2006 (UTC)

The energy does not go into the load; it is reflected back (down the power lines) to the source, and so is wasted. — Omegatron 13:53, 1 September 2006 (UTC)

Current that is not in step with the voltage does not transfer energy from the source to the load but continually circulates energy back and forth between the source and the load. This energy circulation is not 100% efficient. During each "trip" from source to load or load to source, some energy is lost as heat in the wires and other parts of the power generation, transmission and distribution equipment. Does that help? --C J Cowie 14:24, 1 September 2006 (UTC)

Sorry, but this is still not clear. Why would any current not be in step with the voltage? Utilities control the voltage, don't they? I understand some energy is lost as heat, etc., but if we are talking about energy that circulates back and forth, then clearly what is being talked about is something different from that. Or is it? Is reactive power merely the additional amount needed to allow for power lost to heat on the wires etc.? And, why would a device send ANY energy back? I doubt most devices are even designed to do that. And why would wave forms have anything to do with this? 216.239.88.89 (talk) 04:36, 8 October 2010 (UTC)

Could you look at the part that goes

In a purely resistive AC circuit, voltage and current waveforms are in step (or in phase), changing polarity at the same instant in each cycle. All the power entering the loads is consumed. Where reactive loads are present, such as with capacitors or inductors, energy storage in the loads result in a time difference between the current and voltage waveforms. During each cycle of the AC voltage, extra energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric or magnetic fields, and then returned to the power grid a fraction of a second later in the cycle.

and tell us what is unclear in it? --Wtshymanski (talk) 15:07, 8 October 2010 (UTC)

For what it's worth, I found the paragraph above to be exceptionally clear.

The problem User 216.239.88.89 is having is, in my opinion, not caused by the article being unclear but rather from some misconceptions he has picked up along the way. The question "Why would any current not be in step with the voltage? Utilities control the voltage, don't they?" shows this. If a utility outputs a sinewave at a fixed voltage, that means it has it has zero control over the current. Alas, this sort of misconception is not something that can be addressed in a Misplaced Pages article about power factor. He needs to go back and get a good understanding of Ohm's law, first in a DC circuit with a resistive load, then in an AC circuit with a resistive load, then in an AC circuit with a capacitive load. Ohm's law covers all of this quite nicely. Guy Macon 02:50, 9 October 2010 (UTC)

Perhaps ignorance rather than misconceptions. See, for example, I don't understand about a utility outputting a sine wave. I think they output a fairly controlled range of voltages and currents, matching output with load fairly closely. Anyway, I don't have all that education and I suppose it is unrealistic to expect the explanation to make sense when I don't have that. 216.239.78.204 (talk) 22:19, 10 October 2010 (UTC)

What I would hope for is the article having links that lead you to the science that the article is based upon. For an example, look at the article on string theory; it of course cannot explain string theory to someone who has no knowledge of physics or math, but in theory you could drill down through the many links and gain enough knowledge to understand it. I think that the same is true here; power factor links to real power, which in on the page explaining AC power, which links to Mains electricity, which links to Voltage, which links to Ohm's law, which will explain why it is that your belief that utilities "output a fairly controlled range of voltages and currents" is completely and utterly wrong. You will never understand power factor unless you abandon your basic misconception that it is possible to control both the voltage and the current into a varying load. That is simply not possible.

BTW, saying that you don't understand what utilities output would be ignorance. Saying that utilities control voltage and current is not ignorance; it is a misconception. It is the difference between not knowing something and knowing something that isn't true. No shame in either, of course; only a fool thinks that having technical knowledge of a particular topic or never being in error makes them somehow superior. Guy Macon 01:51, 11 October 2010 (UTC)

The energy doesn't necessarily get bounced back and forth, either. It can disappear into the source. — Omegatron 14:42, 1 September 2006 (UTC)

Most of the reactive power flows back and forth between the source and load such that "On one half-cycle, the source supplies energy to the energy-storage element, and on the next half-cycle the energy-storage element returns energy to the source....currents required to supply the stored energy produce losses in the generating and transmission system..." Scott, Ronald E. (1960). Linear Circuits. Reading, MA: Addison-Wesley. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help) “Low power factor means more current and greater ${\displaystyle I^{2}R}$ losses in the generating and transmitting equipment.” Fitzgerald, A. E. (1983). Electric Machinery (4th ed. ed.). Mc-Graw-Hill, Inc. ISBN 0-07-021145-0. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)

Again, I would have to say that it must be ignorance on my part, rather than any misconception. I do believe that utilities try to control the voltage, current, and frequency of the electricity. They deliberately change the voltage at various points, to achieve efficiencies in transmission. They must keep the supply and load reasonably closely matched, so that generators aren't over or under loaded. I know they do try to keep frequency aligned in the grid. So I'm not at all clear why that's a misconception. As for 'apparent power' and 'reactive power', I think it is something you have all learned about so long ago, that it isn't at all obvious to you that the explanation isn't clear to anyone without all that education. Why would a device, say a radio or toaster, reflect any power back? I'm sure it wasn't designed to do that. It might be something inherent in any electrical device, but what? Or, for that matter, why would a device temporarily store the apparent power when no doubt it wasn't designed to do that. They draw a certain amount of real power to do the work they need to do. Where does the other power come in? Obviously there is something called apparent power and reactive power, but it seems it needs a lot of education to be able to understand it. I'm not sure why that is the case. I would have liked a clear explanation. But if it isn't possible, it isn't possible. What, I wonder causes the reactive power to be at various levels? 216.239.77.231 (talk) 04:36, 6 November 2010 (UTC)

216.239.77.231, This is a bit over simplified, but perhaps it will help you. Loads other than 100% resistive loads such as electric heaters or incandescent lights require reactance. A standard motor or capacitor need an injection of energy before they will perform the intended function. For a capacitor it needs to be charged up. For a motor the stator and rotor coils will need to absorb an electrical field. A motor will not turn until all the coils internally are charged up. When you shut off a motor all the store energy in the coils discharge back into the system. This energy is not useful power, but rather a temporary electric field. —Preceding unsigned comment added by 158.106.48.10 (talk) 13:54, 21 November 2010 (UTC)

Merge from Distortion power factor

Distortion power factor should be merged here, it's small and it needs to be given a contenxt which this article already supplies. --Wtshymanski (talk) 15:45, 16 March 2010 (UTC)

Agree --Chetvorno 22:20, 17 March 2010 (UTC)

Agree, and note that the merge has been done. Guy Macon 01:40, 22 November 2010 (UTC)

Negative Power Factor?

I'm having great difficulty with the following wording: The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power, and is a number between -1 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf). Real power is the capacity of the circuit for performing work in a particular time; it can be either positive or negative, depending on whether the power is flowing from the nominal source to the nominal load, or vice versa. Apparent power is the product of the RMS current and RMS voltage of the circuit, which, by definition, is always positive. Which power flow then determines the sign of the power factor? Real or reactive? Apparent power is always positive? Why? Supposing I'm watching the Manitoba to Minnesota tie line and suddenly one of the Nelson River Bipole lines trips...suddenly instead of exporting mumblety-mumble megavoltamperes, the utility is importing mumble megavoltamperes. Would be very tempting to say the sign of the apparent power flow has reversed. Maybe I've been talking to t0o many transmission people, they seem to be more worried about vars than watts. "Lead" and "Lag" I can sort-of understand, I don't know what a negative power factor means in the case of distortion. --Wtshymanski (talk)

If my learned co-editor is in fact who he says he is, I am presuming greatly - but at least I have some references, whereas so far I've seen no references defining 'negative' power factor as 'power factor with watts flowing back into the source'. --Wtshymanski (talk) 04:22, 16 December 2008 (UTC)

I've never seen power factor expressed as a percentage. Could this be a UK/US difference? Biscuittin (talk) 19:59, 2 November 2009 (UTC)

From the Fluke 434 Power Quality Analyzer manual (which agrees with my experience as a working Electrical Engineer):

"Interpretation of Power Factor when measured at a device:"

"PF = 1: all supplied power is consumed by the device. Voltage and current are in phase."

"PF = 0 to 1: not all supplied power is consumed, a certain amount of reactive power is present. Current leads (capacitive load) or lags (inductive load)."

"PF = -1 to 0: device is generating power. Current leads or lags."

"PF = -1: device generates power. Current and voltage are in phase."

In most areas of electrical engineering a negative power factor is rare - so rare that some EEs have never heard of it. There are two areas where negative power factors come into play a lot; electric motors that are braking a massive load (this includes regenerative braking on electric vehicles) and devices that source or sink power so as to correct for overvoltages/undervoltages in a poorly regulated line.

BTW, this has nothing to do with the practice of displaying leading/lagging of a positive power factor with a minus or plus sign. I have seen meters that do this (there is no consistency as to whether leading or lagging gets the plus sign) and it can confuse a technician who also has access to a Fluke 434 that uses a plus sign for both. Guy Macon 17:22, 15 July 2010 (UTC)

We don't usually alter previous editor's headings on talk pages. I would appreciate an authoritative reference for "negative" power factor defined as your meter manual suggests. Those two areas you talk about are pretty darn common in electrical engineering and if there was a wide-spread convention that "negative" power factor means "power flowing back to the source", surely it would be well documented? "Negative" power factor is not described at all in IEE Std. 100, which is a pretty good overview of IEEE standards practice. And there is IEEE Std. 1459, which says (Note 1, section 3.1.1.1) real power only flows to the load and can never be negative. Leading and lagging PF I've seen marked on scales, but "negative" PF is not something I've seen displayed on a power factor meter. There are 4-quadrant electrodymometer type meters, but they don't seem to mark the scaled as "negative". --Wtshymanski (talk) 18:11, 15 July 2010 (UTC)

Re: IEEE Std. 1459, I don't have it in front of me (I am at home) but I suspect that it defines "load" in a way that precludes generators of electrical power.

Re: "Those two areas you talk about are pretty darn common in electrical engineering and if there was a wide-spread convention that 'negative' power factor means 'power flowing back to the source', surely it would be well documented?", you appear to have missed what I wrote: "In most areas of electrical engineering a negative power factor is rare - so rare that some EEs have never heard of it." Again, AC loads that are energy sources are rare, not common.

Re: "but 'negative' PF is not something I've seen displayed on a power factor meter", the Fluke 434 Power Quality Analyzer does exist. I assume that you have only used the usual low-cost PF meters and have never needed something more sophisticated. IIRC, Hotektech, Dranetz and Extech power analyzers also measure negative power factor.

Re: "I would appreciate an authoritative reference for 'negative' power factor defined as your meter manual suggests", here are three, two from the dawn of electrical engineering and one modern. Plus, of course the Fluke manual, which I consider to be authoritative.

From The Electric Journal, Volume 5 (1908):

"Negative Power-factor: When a generator is connected to a circuit having in series only resistance, inductance and capacity, the current cannot be more than 90 degrees out of phase with the e.m.f., but if a synchronous motor (or a rotary converter or another generator) is in the circuit, the difference of the e.m.f.'s of the two machines sends current from the generator through the other machine. the generator is not delivering positive power to the other machine which, therefore, cannot run continuously without changing phase relation, or receiving power from some other source."

http://books.google.com/books?pg=PA480&dq=%22negative%20power%20factor%22&ei=imQ_TLywFpK4sQOZ-cH2CA&ct=result&id=lrESAAAAYAAJ&output=text

From the Philosophical Transactions of the Royal Society of London, Volume 203 (1904):

"The fact that the solid arc has a negative power-factor at frequencies below the critical frequency of 1950 indicates that the arc is under these conditions supplying power to the alternating current circuit, and that this is the fact can easily be shown experimentally by connecting a wattmeter so as to measure the power supplied to the solid arc by the alternating current, when it will be found that at low frequencies the solid arc is actually supplying power to the alternate-current circuit, while at frequencies above the critical value the alternate-current circuit supplies power to the arc. This observation is of course not in any way at variance with the principle of conservation of energy, since the alternating energy given out by the arc is derived from the direct-current energy supplied to it, the arc acting as a converter."

http://books.google.com/books?dq=%22negative%20power%20factor%22&pg=PA322&id=eG0OAAAAIAAJ&output=text

From "Analysis and Performance of 3-Phse Grid-Connected Induction Generator via Transistorized Ac Voltage Controller" EE Dept.- College of Engineering, Cairo University (2008):

"...Accordingly, the generator will absorb active power from the grid, which leads to negative power factor."

http://faculty.ksu.edu.sa/Alolah/Documents/Files%20of%20papers/C033.pdf

From the Fluke 434 Power Quality Analyzer manual:

http://assets.fluke.com/manuals/434_435_umeng0300.pdf

Search for "interpretation of power factor"

Also see:

http://us.fluke.com/fluke/usen/Power-Quality-Tools/Three-Phase/Fluke-430-Series.htm?PID=56077

I would also ask what you would say the power factor is for a line that has the current 180 degrees out of phase from the voltage. That's a test that I have run many times on AC power supplies using another, larger AC power supply as the "load." Some AC power supplies cannot handle such a load. Guy Macon 21:17, 15 July 2010 (UTC)

Not comforting... a student paper that misspells "phase" in the title does not fill me with confidence. A 1908 paper? Physicists? And overhauling loads are described in every undergrad machines lab. --Wtshymanski (talk) 02:39, 16 July 2010 (UTC)

Again I ask; what do you say the power factor is for a line that has the current 180 degrees out of phase from the voltage? Guy Macon 09:45, 16 July 2010 (UTC)

There's no power being transferred to the "load" if the current is going the other way, so it can't be defined. Or, we've got the source and load interchanged, so the PF is 1. Which one do the authorities prefer? This situation arises many times in transmission...some times the electricity runs from Winnipeg to Minneapolis, but some times the electricity runs from Minneapolis to Winnipeg, too. --Wtshymanski (talk) 13:07, 16 July 2010 (UTC)

There's no power being transferred to the load if the load is a pure capacitance, yet we have no trouble determining the PF in that case. You can't just say "it can't be defined." Such circuits exist and they have measurable voltage, current, and phase. If your method of calculating PF cannot handle a particular real-world combination of voltage, current, and phase, yet standard test equipment can, then something is wrong with your method of calculatiing PF. The PF still exists in the real world.

The concept of negative power factor has been in use for over a hundred years. I grant that it is rarely used and many engineers have never heard of it, but the concept of a using a flickermeter to obtain a numeric value for Pst is also something that many engineers have never heard of, yet Pst and Negative PF are measurable by most or all power quality analyzers. (See IEC 61000-4-15 and IEC 61000-3-3).

Invoking IEEE Std. 1459 proves nothing. It specifically defines real power as being only that which flows to the load, and thus by definition cannot be used to describe a circuit where real power flows from the load. Guy Macon 10:23, 17 July 2010 (UTC)

Well, yeah, that's kind of the point; "reliable references" are what we use here on Jimbo's dream. IEEE 1459 is a set of *definitions* of terms used in describing AC power and defines (for those who chose to use it) what "power factor" means. If the committee that wrote up 1459 thought that, for defining power factor, power only flows from a source to a load, that's good enough for me. Are you saying the Fluke company's designer who labelled something 'minus' instead of 'reverse power' is a higher authority than the IEEE? As you point out, power often flows either way down a wire so this is a common situation, and yet i don't ever see anyone calculating a negative power factor in my meager collection of texts. Could you find me a worked example somewhere where a prof is telling his students " -1 MW over +2 MVA means the power factor in this circuit is -0.5, lagging" or something to that effect; preferably an authority who can spell "phase" correctly in the title of a document.

I had a similar discussion with another editor some years ago and asked for some documentation, and he hasn't got back to me yet. If it's defined, why is it so hard to find anyone talking about it? Negative voltage, all the time. Negative resistance, sure. negative power, in some contexts, sure. Negative power factor - only in papers from 1908? Sounds fishy to me. (You can proably find more places talking about power factor greater than 1 than power factors less than 0.) ( I worked in an arc furnace shop so had to get familiar with flicker and flicker meters and the difference between 120 v bulbs and 240 v bulbs...) --Wtshymanski (talk) 13:44, 17 July 2010 (UTC)

If anyone is still interested, IEEE 1459 says "1—The instantaneous power is produced by the active component of the current, i.e., the component that is in phase with the voltage. It is the rate of flow of the energy. This energy flows unidirectionally from the source to the load. Its rate of flow is not negative, pa≥0." which is why IEEE 1459 never discusses "negative" power factor. If P ia never negative and S by definition is never negative, P/S can never be negative. -Wtshymanski (talk) 15:30, 19 July 2010 (UTC)

I'm not a professional, but what seems obvious to me is that the negative power factor is measuring the flow in the direction from what was a load (but is now acting as a source) to what was a source (but is now receiving the flow). Which is why the IEEE 1459 doesn't SEEM to allow for it. The source and load have switched places, but the measuring device is using the same direction as before, and so to distinguish the situation uses negatives. Isn't that what is really happening? 216.239.88.89 (talk) 04:36, 8 October 2010 (UTC)

The output of a Fluke 434 Power Quality Analyzer is a reliable source. It is a standard piece of test equipment used throughout the industry to measure power factor. If it displays a negative power factor, the circuit has a negative power factor. All the other brands of power analyzers will give you the same reading.

You keep quoting IEEE 1459 again and again while ignoring the fact that IEEE 1459 specifically defines real power as being only that which flows to the load, and thus by definition cannot be used to describe a circuit where real power flows from the load. You can't apply an IEEE standard to a circuit topology that the IEEE standard says it does not apply to. Do you have a reference that doesn't specifically exclude the circuit we are discussing?

If, as we have seen, your preferred method of calculating PF cannot handle a particular real-world combination of voltage, current, and phase, yet standard test equipment can, then that in itself shows us that something is wrong with your method of calculating PF. The PF still exists in the real world. You aren't allowed to pretend that when an AC power source has the current 180 degrees out of phase from the voltage suddenly power factor does not exist, nor are you allowed to claim that the power factor is exactly the same as it would be if the load was resistive.

Also, the Philosophical Transactions of the Royal Society of London, Volume 203 (1904) meets every criteria for being a proper citation from a reliable source. Unless you can cite a reference establishing that later research disproved the 1904 research you have no logical reason for rejecting it as a reference. And no, an IEEE standard that clearly states that it does not apply to power flowing from the load to the source does not disprove the 1904 paper.

If you want to claim that the term is rarely used, that's fine. It is indeed rarely used. I worked for many years without running into the term. However, once I started working on programmable AC power sources, I found that it was indeed a valid term, used by engineers in that specialized field and measured by standard test gear such as the Fluke 434 Power Quality Analyzer. Guy Macon 22:48, 23 July 2010 (UTC)

I am looking for a research paper titled "Negative Power Factor" by Allen Varley Astin (director of the National Bureau of Standards until 1969). I know that it is in the Library of Congress, but I have not been able to obtain a copy. Does anyone know of an online source? Thanks! Guy Macon 23:01, 23 July 2010 (UTC)

IEEE 1459 seems to supersede the 1908 paper and is a current technical standard. It's not my definition nor my method, it's IEEE. Take it up with the people who revise 1459 ( which is overdue to be changed from a draft standard). Why do they define real power as flowing only from source to load? The Fluke company is free to make up its own definitions. However, it seems needlessly complex to me - why overload the - sign with the direction of power flow? Are you sure the - sign on the Fluke isn't just an indication you've hooked the leads up wrong? Again, if the concept is useful, it should show up in the current literature, not something written by physicists a century ago. Why don't the other Fluke power quality meters also measure negative power factor - there's only one in the line that has this in the user notes, and to me it looks like an indication of incorrect hookup rather than an attempt to be incompatible with IEEE 1459. I'm not saying the term is rarely used, I'm saying it's never used because it's against the way power factor is defined in IEEE 1459. You're making an awful lot out of your 9single model of) Fluke user manual- if they'd put in an LED saying "Backwards leads" instead of overloading the - sign in the display, would this conversation still have existed? --Wtshymanski (talk) 04:42, 24 July 2010 (UTC)

I'm not sure how to add comments to this discussion, but I will try. As one of the active participants in developing IEEE 1459, I regret that we failed to acknowledge that active power can flow both directions, and has a sign. I will try to get that fixed in the next edition. Negative power is not a matter of connecting meter leads incorrectly; it's a real-world situation. Consider a house that has a large solar panel/inverter on its roof. Let's say that in the middle of the day, the solar panel makes enough power that power flows from the house to the grid. In the middle of the night, power flows from the grid to the house. The simplest measurement solution is to define one of these directions as "positive power" -- typically, we define the power that flows from the grid to the house as positive power -- and that makes the other direction negative power. Anybody who believes that single phase non-distorted power flow is defined by Vrms x Irms x cos(theta) must also believe in negative power, because Vrms is always positive due to the "square" term in RMS, Irms is always positive due to the "square" term in RMS, and cos(theta) can take any value between -1 and 1. I don't think references are necessary for this discussion, any more than we need a reference saying that -1 x 4 = -4 . Of course, power factor can take any value between -1 and +1 - there isn't any doubt about this topic in the electric power measurement community. Every modern electric power instrument for AC systems that has been built in the last quarter of a century happily measures both negative and positive power (Fluke, Dranetz, BMI, Schneider, Power Standards Lab) and calculates a signed Power Factor value as the ratio of a signed power to an unsigned VA.AMcEachern (talk) 23:03, 12 October 2012 (UTC)

How am I supposed to interpret a "negative" pf, which according to IEEE 1459 can't happen? Say I walk into the control room of a hydro plant and I see the big power factor meter on the wall reads "-0.75" . What do I do? Do I adjust the wicket gates to pump power back into the system, or do I raise (or lower) the excitation? What does the -ve sign mean? Isn't it more correct to have one meter saying "lead or lag power factor" and another meter saying "import or export power" - a two-dimensional measurement needs two pointers, not one. --Wtshymanski (talk) 01:05, 13 October 2012 (UTC)

Again, I regret the error in IEEE 1459. You are very helpful in pointing out this misunderstanding, and that's exactly why these Standards go through revisions to create new editions. (For example, IEC 61000-4-30, Power Quality Measurement Methods, which I Chair, is preparing its third Edition; despite being heavily used for 10+ years, this standard still needs clarification, correction, and extensions. IEEE 1459 is in a similar state.) To answer your specific question about a control room of a hydro plant: it would be unthinkable that there would ever be negative power for such a hydro plant i.e. it would never be accepting power from the grid, unless, of course, it is one of those rare pumped-storage systems in which the electrical rotating machinery is used both as a motor to drive the pump, and as a generator when the water flows downhill. Very, very rare. But the question at hand, I think, is about the definition of Power Factor and not about a specific application in a generating plant. With your permission, I would like to break the definition down and respectfully ask you which of the following statements you disagree with? For the purposes of these statements, let's assume together the simplest possible situation: a single-phase system in which both the voltage and the current are perfectly sinusoidal. (1) RMS values are always positive, because they begin by squaring some either positive or negative instananeous value, and the squaring function converts both to a positive number. (2) Volt-Amps is RMS volts x RMS amps, and is therefore always positive. (3)Power Factor is the ratio of Watts to Volt-Amps. (4)for sinusoidal waveforms, Watts is RMS volts x RMS amps x cosine(angle between voltage and current sine waves) - this is mathematically equivalent, for sinusoidal waveforms, to watts is the integral, over an interval of time that is an integer multiple of half-periods, of the instantaneous product of the instantaneous voltage and the instantanous current. (5) The cosine function has an output in the range of -1 to +1. (6) Watts, therefore, can be either positive or negative. (7) Power Factor, therefore, has a range of -1 to +1. Please, can you identify which of these statements you disagree with? There may be more than one, of course. Thank you! AMcEachern (talk) 21:11, 14 October 2012 (UTC)

The bit where the cosine goes negative. This can only happen if power is flowing from the "load" to the "source" . IEEE 1459 currently says (in very small print, too), power, by definition, flows only from source to load. As long as some people define "lead/lag" to mean "plus/minus" and others get "forward/backward" to mean "plus/minus", generalizing the present IEEE 1459 definition to include "reverse power" is not going to help clarify the situation. AC power is inherently a two-dimensional quality and squashing it down to a one-dimensional representation is going to be wrong much of the time. I don't want a hydro operator reaching for the wrong knob when he sees "negative" power factor. I look forward to a new edition of IEEE 1459 that explains this authoritatively, though it's a little like trusting the next Windows security update (if they didn't get it right in the last edition, what confidence should we have in the new release?). Once IEEE 1459 is fixed and the world agrees on it, Misplaced Pages can cite it as a reference and the world will be a richer, more confusing, place.

The other place where you get a hydro unit absorbing power from the system is when it is in synchronous condensor mode, spinning the turbine in air (with some gimmick to keep water out of the turbine); this is only a few per cent of the unit rating, though. The watts are negative, but it's still sending leading vars to the system - what is the sign of the power factor then? --Wtshymanski (talk) 22:25, 14 October 2012 (UTC)

Ah! I think you have it precisely correct when you put "load" and "source" in quotation marks. Your interpretation is absolutely correct - power is negative when it flows from the thing identified, nominally, as the load towards the thing identified, nominally, as the source. A quarter of a century ago, that was an extremely rare situation; today, it's far more common, with so many residences having photovoltaic systems. At their revenue meters, we see positive power when power flows from the grid to the house, and negative power when it flows from the house to the grid. There's nothing complicated about that. You are also correct that the old convention of using "+" and "-" for lead/lag causes a lot of confusion, but fortunately this is also rare today -- not rare enough, probably! But as long as we all agree that power factor is the ratio of power to volt-amps, I don't think there's any real dispute that power can be negative (at least among modern measuring authorities) so I don't think there's any real dispute that power factor can range from -1 to +1. Alex Emanuel (Chairman of IEEE 1459) has asked me to organize a debate on AC power definitions at the 2013 Summer Meeting of the IEEE Power Engineering Society. I will make sure that your point about the names of the source and load is clearly presented, if you're not there to present it yourself, which would be very welcome. (Regarding your question about the synchronous condenser mode, if the watts are negative, the PF is negative; but in this case it's a very small negative number, because we're seeing mostly VAR's so the ratio watts to volt-amps is very small.) If I may add one other note: in DC power systems, the concept of negative power is quite common. For example, measuring the power at the terminals of a rechargable battery, it's conventional to measure negative watts while the battery is being charged, and positive watts while the battery is delivering power. As you point out, this is a matter of reversing the "load" and the "source". But this is so common in DC power supply design that there isn't any discussion -- it happens with capacitors, super capacitors, batteries, inductors, or any other component that can store and release energy. The signs of the DC voltage and the DC current determine the direction of power flow; if the signs are the same, the power flow is positive, and if the signs are opposite, the power flow is negative. And one more small note -- if we consider a single-phase sinusoidal-voltage-and-current power circuit with non-unity (but positive!) power factor, surely everyone agrees that the power is positive during part of the cycle, and negative during a smaller part of the cycle? It's positive during the part of the waveform where the voltage and current have the same sign, and it's negative during the part of the waveform where the voltage and current have different signs. So even on common AC systems, negative power is quite ordinary during part of the cycle...AMcEachern (talk) 01:03, 15 October 2012 (UTC)

There's no charge number for sending me to IEEE meetings, so that's not going to happen. The (magnitude of the) power factor of a synchronous condensor is still in the range 0 to 1, no matter how small the watts consumed by the unit. DC circuits are out of context in a discussion of power factor. The IEEE 1459 definitions aren't talking about sub-cycle flows, only the average over integral numbers of cycles.

Negative power is a perfectly useful thing to define, sometimes the power flows from Winnipeg to Minneapolis, sometimes it flows from Minneapolis to Winnipeg, it's perfectly legitimate for the utilities at either end to define power coming in as "plus" and power going out as "minus". Only a Wikieditor would be confused at the resulting ambiguity of the sign of the power flowing in the line - it's purely a matter of definition and Manitoba Hydro and Xcel Energy define it differently for their own purposes.

I look forward to a new edition of IEEE 1459. I thought it was admirably clear when it said "Power flows from sources to loads" and therefore doesn't need to define negative power or negative power factors. I don't think it's useful to define "negative power factor" as "power factor with source and load interchanged" because I think it's overloading the "-" sign with a whole different meaning. A single number can't tell you everything you need to know about power flow; you need to know two dimensions, real/reactive and import/export, to properly characterize it.

This is getting off topic for a Misplaced Pages article talk page because until there's a new citation for negative power factor, there's no way to change the article to include a concept of "negative" power factor. --Wtshymanski (talk) 14:39, 15 October 2012 (UTC)

Thank you. I appreciate your intellectual honesty in acknowledging that negative power is a useful concept, and I appreciate your writing that you don't think it's useful to define negative power factor, acknowledging (I think!) that this is your opinion, backed of course by your reading of IEEE 1149 that negative power does not exist. I'm not sure how to reconcile these two ideas, if one accepts that the definition of power factor is the ratio of watts to volt-amps, but I am grateful for the progress.

It will take a couple of years to get the error out of IEEE 1149; to speed things up, I will compose a paper for IEEE Transactions on this issue, but that too will take a year or so to get drafted, submitted, peer-reviewed, and published.

Meanwhile, based on the discussion above, and based on the citations above, and based on the practice of all the major instrument manufacturers for the last quarter of a century, would you consider changing the first line of the article from "...is a dimensionless number between 0 and 1..." to "...is a dimensionless number between 0 and 1 (or, according to some authorities, between -1 and +1)..."? I think you could make this change without compromising your intellectual integrity, and it certainly would add a useful flag to readers that there is honest disagreement about the question. Respectfully, AMcEachern (talk) 15:44, 15 October 2012 (UTC)

It should be noted that the IEEE are not the only body who get to decide on these matters. They are a very small cog in a global wheel. Having said that, I am not aware of any body that has said anything different, but the point is that some governing body could without running it past the IEEE first. If the Society of {insert some tin pot little country here} Electrical Engineers made such a statement, it would be citeable regardless of what the IEEE has to say on the matter. 86.159.159.194 (talk) 15:56, 15 October 2012 (UTC)

Cite it and write it. I quoted IEEE 1459 two years ago in the discussion above (see the remark above the 19 July 2010 .sig line). I would be pleased to see an authoritive source quoted that generalizes power factor to -ve values, but the instruction manual for someone's meter isn't on the same rank as an IEEE standard. --Wtshymanski (talk) 16:24, 15 October 2012 (UTC)

Would you accept IEEE 1459 itself as the citation for positive and negative power, and therefore positive and negative power factor? if so, please examine Figure 1 in both Editions of IEEE 1459, which clearly shows both positive and negative power along the horizontal axis. I agree that Figure 1 directly conflicts, in the same Standard, with the statement in 3.1.1.1 that says that power is always positive. But surely that conflict makes my point: that Misplaced Pages should not deprive its readers of the fact that authorities disagree?

Again I ask, based on the discussion above, and based on the citations above, and based on the practice of all the major instrument manufacturers for the last quarter of a century, would you consider changing the first line of the article from "...is a dimensionless number between 0 and 1..." to "...is a dimensionless number between 0 and 1 (or, according to some authorities, between -1 and +1)..."? I am not asking you to say anything that is untrue; I am asking that you allow Misplaced Pages readers to know that your opinion is not the only opinion, and that there are reasonable published references that disagree, and reasonable authorities that disagree, and even parts of IEEE 1459 that disagree. AMcEachern (talk) 00:34, 16 October 2012 (UTC)

We can't say "according to some authorities" on Misplaced Pages, without pointing at "which" authorities we mean. There must be a textbook somewhere (preferably not published by Tab Books) that gives an example of negative power factor calculation. This should be easy to cite. --Wtshymanski (talk) 02:37, 16 October 2012 (UTC)

Thank you, and I truly appreciate the progress we have made in this discussion.

(I have temporarily placed a Draft IEEE paper at http://powerstandards.com/Shymanski/draft.pdf for your review; it includes a dozen citations over the last 100 years on the correct meaning of negative power factor. I would welcome your comments and suggestions. Among my colleagues in the academic and metrology community who have seen this draft, the general consensus is that the paper is correct but perhaps not worth publishing, because it is so widely known and accepted that power factor ranges from -1 to +1. And one professor of Electrical Engineering at Berkeley, who wants to remain nameless, jokingly asked me not to correct the Misplaced Pages article on PF because she uses it in her introductory lecture as a great example of why her students are forbidden to cite Misplaced Pages - there's an obvious technical error -- the range 0-1 -- on the very first line of the article...)

May I gently point out that we have no citations, as far as I know, for saying that power factor is between 0 and 1? My understanding is that you derive that conclusion from the statement in IEEE 1459 that power is always positive. Based on the same level of analysis, could we use IEEE 1459 Fig 1 (which shows positive and negative power) as our citation for negative power factor? Would that be a reasonable solution? AMcEachern (talk) 18:18, 17 October 2012 (UTC)

The cleanest way to fix this is to fix IEEE 1459, but if the standards committees let the current language persist through the last two editions, it's obviously of more concern to Wiki editors than to working engineers. If I see a "-" sign on a power factor meter I've hooked up, I either start looking for an electrican to swap wires around, or else I think thre's something unexpected going on in the power system. How useful is a "negative" power factor? It's not like you can do arithmetic on power factors - you can't say "This branch is -.8 pF and this branch is +.9, so my total power factor is .1 and all's right with the world". It's like the bloody "humidex" or "wind chill" numbers, which try to give a one-dimensional figure for a two-dimensional situation, simplifying nobody's life but those of the radio DJ's. But I've said all this before. --Wtshymanski (talk) 19:10, 17 October 2012 (UTC)

Most of the analogue power factor meters that I have encountered, both single and three phase, have a scale that occupies the full 360 degrees of a circle. The quadrants are marked 'lead' and 'lag' (two of each). Although the opposite quadrants are not marked as 'positive' or 'negative', nevertheless an indication in one (say) 'lag' quadrant represents power flowing in the opposite direction to when the instrument reads 'lag' in the diametrically opposite quadrant. Although power factor in itself cannot be negative, this would equate to the concept of negative power - that is power flowing in the opposite direction to that which is regarded as positive. Obviously, the concept of negative power is absurd in its own right. On the other hand, digital power factor meters generally do not indicate negative power factor as such (though from the above, this does not seem to be universal). Like negative power, negative power factor seems to be just a mere convention to indicate that power is flowing in the opposite direction. The only problem with the concept is that if P=V.I.cosΦ, the current flowing the other way can also be considered negative, thus P=V.-I.-(cosΦ) which will yield a positive power, undermining the concept (though of course power cannot really be negative so it works in convoluted sort of way).

Watt-hour meters, when energy is passed back into the grid, will run backwards raising the alarming concept of negative energy and hence negative power - once the concept of negative time is eliminated (don't even think of going here - it will do your head in). But we can all relax, it is really positive energy just passing in a different direction. At the end of time, it all ends up as heat warming up a rather chilly universe (OK- that's a simplified view - please don't start a discussion on energy utilisation in the universe either!). DieSwartzPunkt (talk) 17:07, 13 October 2012 (UTC)

Power Factor for the Modern World

Wtshymanski has removed the section I added with no adequate response to my explanation. I am new to contributing to Misplaced Pages pages and am trying to learn the ropes quickly. I appreciate the spirit and goals of Misplaced Pages and do not want to degrade their mission. I am a physicist who has probably spent more hours over the last 30 years designing and experimenting with active power factor compensation than anyone else. I have founded 3 companies that design, manufacture and market this equipment and am currently the CEO of one of these companies so conflict of interest is definitely a possibility here. I am a recognized expert and innovator on this subject and was recently asked to give a presentation at EPRI's annual conference which took place in Quebec last June. My work is mostly a labor of love as I am genuinely trying to contribute to solving the world's electrical power problems so that we evolve into something that is more sustainable. To do this, my companies have to become very successful financially and that has certainly been the case with Heart Interface, Trace and Xantrex (now Schneider) which all just reeks of conflict of interest. However, the world has changed and power factor, which used to be a more esoteric engineering subject, has become something that is effecting most people's lives in ways they don't understand. Understanding this, by people with no engineering background, is a legitimate function of Misplaced Pages. Although the grid is a complex mix of loads, each load, by itself, consumes some small amount of power and creates some small amount of transmission loss in the entire system, including the windings of the massive grid generators and transformers. The grid has to pay for all of this energy and the losses so you can see that low power factor loads cost the grid more per kWh to provide than do high power factor loads. With the massive migration to CFL lighting and the great abundance of computer power supplies the grid is having to absorb increased costs which they ultimately pass on to the customer. There are some articles about this that appear in EDN and EETIMES and other engineering publications but the general public is generally not aware that this is even an issue yet they are the ones who are buying and installing these low power factor devices. Since they are ignorant of the issue they do not create any pressure to address it. So, if they somehow hear that it might be an issue and don't even know what "power factor" means they might go to Misplaced Pages. If all they get is a very technical, engineering and very correct and precise article, they will most likely not even read it. So, what might seem redundant to someone educated in electronics, might be the only thing that a non-engineer even reads.

What are the guidelines to adding external links and references at the end of the article? Please respond. Heart141 (talk) 14:05, 27 July 2010 (UTC)

Wtshymanski's comment on his talk page is revealing: "Blanked the page again; tired of getting S*T upon by strangers." He makes quite a few deletions that make people angry, and has limited interest in engaging with them about the deletions. The thing is, most if not all of his deletions make Misplaced Pages better, and a lot of people really are unreasonable when they find their material deleted, so it is hard to find fault.

I reviewed the material that you added and he removed, and I would have removed it had I noticed it first. For example, "This power factor issue is so critical that the Transverter remote panel continuously displays power factor and the included software uses the internal data acquisition to display real time pictures of the wave shapes" sounds like an ad for the Transverter PS, not like an encyclopedia article about power factor. If you work for the company that makes the Transverter PS, you should avoid adding info about the Transverter PS to Misplaced Pages pages. Instead you should go to the talk page and say "I am considering adding the following..." and ask for discussion. Another clue is that your essay goes on for quite a while without any citations, and is written in a folksy manner. Example: "t doesn’t have to be this way..." That's an editorial opinion, not an encyclopedic fact supported by a reference to a reliable source.

Experts on a particular subject matter can be a huge help in improving Misplaced Pages articles, and I don't want to discourage you in any way, but you need to learn how to do things the Misplaced Pages way. Here is a great place to start:

http://en.wikipedia.org/Wikipedia:List_of_guidelines

If you are interested in discussing any of this with me, I welcome cold telephone calls from other folks who work in the area of product development. My phone number is on my webpage (www.guymacon.com). Guy Macon 10:25, 4 August 2010 (UTC)

I've made many edits, 95+% of which were without controversy. I'm interested in editing articles, not in carrying on debates. We don't debate on Misplaced Pages, we find references. I have finite time to spend, as do we all. Everyone who contributes to Misplaced Pages gets the notice that their contributions will be ruthlessly edited by strangers. "If you can't stand the heat...", etc. - I certainly have had edits I've made ruthlessly altered by others; and often for the better. --Wtshymanski (talk) 13:43, 4 August 2010 (UTC)

I agree with all of the above, which is why I wrote " most if not all of deletions make Misplaced Pages better, and a lot of people really are unreasonable when they find their material deleted, so it is hard to find fault " What you do and how you do it is very valuable, and I wouldn't change you even if I could.

I, on the other hand, am willing to take the time to try to educate well-meaning newbies who don't understand why Misplaced Pages is the way it is in the hope of turning them into valuable contributors. To do this I had to address Heart141's stated objection that "Wtshymanski has removed the section I added with no adequate response to my explanation." Heart141 needs to learn that you have no responsibility to respond to him, but rather it is his responsibility to learn and follow the Misplaced Pages guideline that he violated, leading to you removing his edit. I am sure he means well, and could become a valuable contributor if he is willing to learn what is and is not acceptable here. Guy Macon 22:12, 14 August 2010 (UTC)

Cosinus phi mentioned in image caption

Cosinus phi mentioned in image caption, but nowhere in the article (unless I missed it). Can someone clean this up? Thanks. --Xerces8 (talk) 09:15, 8 September 2010 (UTC)

It's "cosine" in English, and it's described under the heading "Definition and calculation". --Wtshymanski (talk) 13:43, 8 September 2010 (UTC)

Archived threads

Anything that hasn't had any commentary for more than a few months, I've moved to an archive page. Re-reading old comments sometimes is useful as a check on the "progress" of the article's contents. --Wtshymanski (talk) 15:45, 8 October 2010 (UTC)

The section on Negative Power Factor is probably ripe for archiving. No consensus was reached, and nobody new has chimed in with any input, so the article remains as it is. (That's fine by me, BTW; it's how Misplaced Pages works.) Anyone disagree? Guy Macon 01:59, 11 October 2010 (UTC)

Just in case any more contributors had something to add, I left it here. I was more concerned about stuff that in some cases was years old. --Wtshymanski (talk) 16:20, 11 October 2010 (UTC)

Splatco

So what does Splatco tell us that's not already in the article and that can't be written into the article? External links are not a substitute for encyclopedia articles - everybody knows how to use Google already. --Wtshymanski (talk) 14:50, 21 February 2011 (UTC)

First, the edit comments are upside down on the burden of proof. The person who wants to add material to an article needs to justify it -- not the person who challenges material.

Second, the SPLat EL does not add to a technical understanding of the article. Most topics are already addressed, so the link is largely redundant. The "It ain't necessarily so!" nonlinear load section is problematic. I would exclude the link on technical grounds.

Third, the SPLat EL has a consumer-related discussion at the bottom (Power factor, consumer electricity costs, and scams) that the current article does not address. That is the EL's advantage (an EL should have material that is not yet included in an article). The section is short and has some issues. The EL page's first link is circular: the SPLat page refers to the open4energy page and open4energy refers to the SPLat page. They even have some identical text and figures. Consequently, I'd be leery of including either - but I'd prefer the open4energy page because it doesn't have the nonlinear load problems. The consumer issue, however, would be adequately served by including the NIST page as an EL, and I've added the NIST link to the article.

Consequently, there is no reason to include the SPLat EL.

Glrx (talk) 17:03, 21 February 2011 (UTC)

Load

The article would benefit by adding a definition of or explanation of 'LOAD'.-- 11:59, 7 March 2011 Twinkletoos

Misleading Statement

"Correction equipment may be installed by individual electrical customers to reduce the costs charged to them by their electricity supplier" I believe this statement is very misleading, Implying that if you increase your pf to unity you will reduce your current consumption. Whole current meters, which are generally used in residential installations measure only active power. Any change in power factor does not change the active power measured by the meter, therefore there is no increased cost in having a low pf. Some utility might charge you for having a low pf, but generally only applies to industrial installations. What are other peoples thoughts? --202.168.24.162 (talk) 02:15, 5 April 2011 (UTC)

Costs, not current consumption. For the sort of customer that gets charged for reactive power, power factor improvement also reduces costs. If you're being billed only for kwh, your consumption is so small that the utility doesn't care (within broad limits) what your power factor is. If you're an industrial customer whose bill includes kva as well as kwh, then you have incentive to improve power factor. --Wtshymanski (talk) 03:04, 5 April 2011 (UTC)

as it reads, one might think "me being a individual electrical customer, i therefore can reduce my electrical costs by installing correction equipment" which is incorrect. I believe the statement needs to be reworked to incorperate that as an electrical customer being billed for kVA, generally industrial, it is beneficial to correct your pf above the minimum outline by the utility to avoid penalties (increased costs). Just recently in Australia power factor equipment was being advertised to the residential consumer as a means to reduce your power bill. It came out in the wash after an investigation from TV show, Today Tonight that active power consumption, which is what was being billed, did not change and that power factor correction did not reduce power consumption. Misleading, i think so --Mpleets (talk) 04:05, 5 April 2011 (UTC)

You should only watch television for the jokes. We should probably rely on electrical customers being able to read their bills - if they aren't paying for low power factor, then they don't get any cost saving from improving it. People who don't edit encyclopedia articles are amazingly pragmatic about not doing things that don't matter. --Wtshymanski (talk) 14:21, 5 April 2011 (UTC)

about Synchronous condensors

In the paragraph "Power factor correction of linear loads", the Synchronous condensors are mentioned "Synchronous condensors are often used in connection with high-voltage direct-current transmission projects......". Is the power factor (and power factor correction) valid for the DC power network ?--Wolfch (talk) 15:08, 5 June 2012 (UTC)

You cannot correct power factor in a DC circuit, because there is no power factor to correct (which I suspect you had already figured out). However, where the DC is produced from AC using a rectifier station, it is often necessary to correct the power factor for the load provided by the rectifier to the AC supply. 86.159.159.194 (talk) 13:03, 14 October 2012 (UTC)

An illustration of distortion power factor

Evidently whoever did the firmware for the Fluke 192C thinks power factor only goes from 0 to 1 inclusive. I had a chance to try one out and set up this demonstration mostly because I was curious about CFL lamps and also curious as to what happens when the current is reversed. I was delighted at the results, of course. (My wall plug power shows some flat-topping - about 2.5% 3rd harmonic according to the Fluke.) --Wtshymanski (talk) 02:11, 17 October 2012 (UTC)

I suspect that you have hit the nail on the head. The most obvious and simplest way of designing the firmware is to multiply the instantaneous voltage by the instantaneous current at each sampling point and average over the cycle (this gives the actual power). Then calculate the RMS voltage and RMS current over the cycle. Multiplying these together gives the VA. Dividing the former by the later gives the power factor. Now the only problem with this arrangement is that power will become negative if it flows 'the wrong way', but VA will remain positive. Thus the power factor will also be negative.

But if instead you substitute an algorithm that will report a negative VA if the power flows the wrong way (the one above will never do so), then the power factor will always come out positive. Having the sign of the VA matching that of the power makes more sense than having a mismatch and the power factor reporting as negative.

Trying a similar experiment to you, I tried it with one of those plug in power and energy monitors. At first, I thought it was not going to tell me anything because: why would it have a negative sign in the display? But it does. Lashing it up the wrong way round, it displays negative power, but positive VA. It displays negative power factor and thus (perhaps not so unsurprisingly) negative energy. At least it didn't display negative time! The specification sheet does not mention its ability to indicate negative quantities. But: this is all original research. 86.159.159.194 (talk) 11:41, 17 October 2012 (UTC)

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