Talk:Power factor/Archive 2

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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.

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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

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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

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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

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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

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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)

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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)

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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)

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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)

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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, Wikipedia 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 Wikipedia 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.

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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 Wikipedia 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 Wikipedia 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 Wikipedia, 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 Wikipedia article on PF because she uses it in her introductory lecture as a great example of why her students are forbidden to cite Wikipedia - 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 [incorrect, with my apologies] 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)

I'm not sure I understand your position on this matter. Could you clarify? In your last entry, you seemed to say that the issue was a lack of citations on negative power factor. I asked you if we could use IEEE 1459 Figure 1 as the citation, but you ignored my question. I provided you with 12 citations on negative power factor in the Draft IEEE paper, and you made no comments. Please, is the issue, in your opinion, a lack of citations?

Could you clarify? I though that you now agreed that IEEE 1459 contains both an [incorrect, in my opinion] statement that power is always positive, and also a [correct, in my opinion] statement in Figure 1 that power is either positive or negative. And I thought you agreed that PF=W/VA. So isn't it clear the IEEE 1459 provides justification both for the argument that PF is in the range of 0 - 1, and also justification for the range of -1 - +1?

Could you clarify? Are you now saying that you believe that we have sufficient citations to, at a minimum, include both ranges; but now you don't understand why including the latter range is useful? If so, here is a response.

(a) You are correct - summing power factors doesn't make sense. If you have two circuits that have PF's of +0.7 and +0.8, together they don't have a PF of 1.5. But I don't see how your true statement relates to the negative power factor.

(b)Negative Power Factor is useful because it conforms to the standard sinusoidal equations PF=W/VA and W= VA x cos(phi), without any exceptions or exclusions.

(c)Negative Power Factor is useful for understanding modern "loads" that are bi-directional (for a very practical example, see Figure 1 in the Draft IEEE paper link above - the positive PF tells you about the behavior of the battery charger as a load, and the negative PF tells you about the behavior of the inverter as a source.)

(d)You are incorrect -- forgive me for being blunt -- that using a polarity for a value that can, in fact, be positive or negative such as the ratio W/VA alters it from a one-dimensional value to a two-dimensional value. Doing so simply places the value correctly on the number line, either to the left of zero or the right of zero. Ratios are often negative - there are negative percentages, for example. Ratios are, by their nature, values with single dimensions. (

e) Lastly, and most importantly, like most metrology engineers I believe being truthful and correct is inherently useful. And I think this is especially important in defining basic measurement quantities. Young engineers use Wikipedia for their initial information - we know they shouldn't, but they do. We older engineers should work hard to make the information in Wikipedia correct. That means, I think, including information with which we personally disagree, but for which there are reasonable technical arguments and which are supported by reasonable authorities as shown through the citations.

At this point, I think I have done the best I can. I have provided you with technical citations from the IEEE 1459 standard, while acknowledging that the standard [which I edited, so I must take the blame] is ambiguous; I have provided you with a dozen citations; I have suggested that both ranges be presented; I have provided you with practical applications. If, in your opinion, all this is insufficient to even include in the article the possibility that there are multiple opinions, you have greater intellectual confidence than I do.

But, still, I'm an optimist -- I do hope you will find a way to, at a minimum, include both the 0 - 1 range and the -1 - +1 range, using all of the proposed citations that have been given to you for justification. Otherwise, we can look forward to continuing this conversation in a few years, after the next edition of IEEE 1459! Cheers! AMcEachern (talk) 22:00, 17 October 2012 (UTC)

Arbitrary Section Break 6

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)

As a professional metrology engineer who specializes in electric power, I am a bit dismayed by the post above. How can one respond to the statement "Obviously, the concept of negative power is absurd in its own right."? Well, gosh. Negative power, in AC power systems, is an (almost) universally accepted concept, and has been for a hundred years or so. Please see the Reference section of http://powerstandards.com/Shymanski/draft.pdf for a dozen examples. Negative power simply means power that is flowing in the opposite direction from the "normal" direction. A classic example, found in Figure 1 of that paper, is a large-scale grid-connected battery: when the battery is being charged, the power flow is positive; when the battery is supporting the grid through its inverter, the power flow is negative. Nothing complicated or absurd about that. Or look at Figure 1 in IEEE 1459, which clearly shows both positive and negative power on the horizontal axis. Regarding the comment about P=V.-I.(cosΦ) -- you've probably forgotten that the "V" and "I" in that equation are the RMS values, and are therefore always positive. RMS means root-mean-square, and any value that is squared is positive. There's no such thing as "-I" in an equation where the I is an RMS value. In electric power systems, there's nothing complicated about "negative energy" either - for example, that's the energy for which the utility pays the homeowner when the homeowner's photovoltaic array is pumping power back into the grid. Yes, correctly-designed watt-hour meters run backwards in this case - that's exactly what they're supposed to do (although modern watt-hour meters segregate positive watt-hours from negative watt-hours, because each typically has its own price per kilowatt-hour). I don't feel as uncomfortable with your dismissal of negative power factor as "a mere convention" -- I suppose the same thing could be said about negative voltage, or a negative rate of interest -- but I am deeply uncomfortable that the first line of this article contains a technically false statement, i.e. power factor is in the range of 0 to 1. (That's the equivalent of saying that all voltages are positive, and dismiss negative voltages as a mere convention that can be fixed by flipping the leads on a voltmeter...) AMcEachern (talk) 14:28, 18 October 2012 (UTC)

As a compromise, what about adding something like this to the article: "Power in electrical circuits is a signed quantity; negative power represents power flowing in the opposite direction from positive power. Some PF meters have a dial that can indicate both the PF and the direction of power flow." or words to that effect. According to DieSwartzPunkt, that much can be supported by sources, and avoids getting into the issue of "negative" PF. --Chetvorno^TALK 21:08, 17 October 2012 (UTC)

I appreciate your effort to find a compromise. The problem, I think, is that there really isn't any issue about "negative" PF among the professional AC power metrology community. PF is defined as the ratio of watts to volt-amps - everyone agrees. Volt-amps is defined the product of RMS volts and RMS amps - everyone agrees. RMS is defined as root-mean-square, and the "square" in the definition means that RMS values are always positive - everyone agrees. That means volt-amps are always positive - everyone agrees. Watts can be either negative or positive - there seems to be some confusion in this group about this issue, but in general everyone agrees about that (for a further discussion, and 100 years of references, please see the draft I've posted at http://powerstandards.com/Shymanski/draft.pdf). Therefore, Power Factor, the ratio of watts to volt-amps, can be either negative or positive. It isn't complicated - everything is rooted in the definitions, and the definitions are well accepted. There's no reason to avoid negative PF. Doing so misleads non-professionals who look at this page for guidance.AMcEachern (talk) 14:28, 18 October 2012 (UTC)

Arbitrary Section Break 7

I am heartily fed up with students telling me that negative PF does not exist, they always quote Wikipedia in support of this. I was surprised to find this discussion which seems to provide incontrovertible proof that the article is wrong, and yet no action has been taken! I have decided to take it upon myself to implement the change using the exhaustive references already provided by Sandy McEachern who is, after all, the acknowledged expert. I do hope that this is not seen as a controversial move, but the continued major inaccuracy in this article cannot be tolerated. JohnJuliusFeinstein (talk) 11:47, 17 March 2013 (UTC)

I must apologize. I thought we had corrected this page long ago. Perhaps someone changed it back and I didn't notice?

You were correct in fixing the article. This goes back to Wtshymanski's original claim that there is no such thing as a negative power factor, and my attempts to correct his error. --Guy Macon (talk) 14:07, 17 March 2013 (UTC)

"When I use a word, Humpty Dumpty said... it means just what I choose it to mean neither more nor less." IEEE 1459 says power factor is positive. You may find it useful to define otherwise but the IEEE seems to think otherwise. --Wtshymanski (talk) 17:44, 17 March 2013 (UTC)

I believe that the reliance on an errored IEEE 1459 has been thoroughly discredited, All the King's horses and all the King's men - Couldn't put Humpty together again! They must also not be allowed to prolong this error. ElectricTattiebogle (talk) 18:09, 17 March 2013 (UTC)

Wtshymanski, it's OK to admit that you were wrong. You made a claim that there is no such thing as a negative power factor. You were wrong. Learn from your mistake and move on. IEEE 1459 is not a suicide pact. Once we know that it has an error in it, we do not have to repeat the error on Wikipedia. We just have to cite the sources that show that it has an error.

From the Fluke 434 Power Quality Analyzer manual:

"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."

That seem clear enough to me. --Guy Macon (talk) 19:53, 17 March 2013 (UTC)

Wtshymanski, please WP:TALKDONTREVERT. There is an overwhelming consensus against you. If you continue to edit war instead of discussing the merits of your argument you will be blocked. Again. --Guy Macon (talk) 20:38, 17 March 2013 (UTC)

I don't even know why there's an IEEE when some nameless technical writer is a recognized authority in the field. Mind, you have to pick *which* Fluke instrument you believe, as my trials with the Scopemeter a few months ago demonstrated. Mr. McEchern says he's going to have the IEEE fix 1459 to match the Wikipedia at a conference this summer. --Wtshymanski (talk) 20:40, 17 March 2013 (UTC)

If by "have the IEEE fix 1459 to match the Wikipedia" you mean make it match your theory that there is no such thing as negative power factor, please explain why he wrote "Therefore, Power Factor, the ratio of watts to volt-amps, can be either negative or positive. It isn't complicated." at the bottom of Arbitrary Section Break 7.

While you are at it, please explain what the power factor is for a line that has the current 180 degrees out of phase from the voltage. That's a test that is performed on every Pacific Power Source AC supply using another, larger AC power supply as the "load." P.P.S. supplies handle this just fine, but some AC power supplies which I will not name cannot handle such a load. So what is the PF in that case?

If 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 circuit 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 that 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. That's clearly wrong. --Guy Macon (talk) 21:35, 17 March 2013 (UTC)

Our resident edit warrior, Wtshymanski seems determined to have his way regardless of what others may believe (I gather that there is no change there). JohnJuliusFeinstein added a section on negative power factor and nobody can deny that it is well reference as he provided no less than twelve (yes, 12) supporting references to support his edit (exactly what Wikipedia demands). Wtshymanski seems determined to stick to his single source that because the IEEE says there is no negative power factor, then every one else must be wrong. Reading this extended discussion, there seems to be plenty of evidence of the concept of negative power factor (and no shortage of instruments that actually display it). The addition of so many rerences in support of negative power factor, along with the overwhealming concensus in this talk page should be the end of the matter. But oh no! Wtshymanski carries on the edit war by wrongly deleting the well sourced addition sticking to his single source, the IEEE, who increasingly seem to be in a minority of one. I B Wright (talk) 10:33, 18 March 2013 (UTC)

• Comment. WP does not choose sides. It sounds like there are two definitions of power factor given by prominent authorities, so both should be reported and neither should be discarded. There's the general idea of PF, and then there are mathematical definitions. I would suggest stating the IEEE definition (provide a date) and pointing out that it doesn't have a negative value but does not specify direction. Then provide the other definition of power factor (possibly providing later dates) and show its merits. Glrx (talk) 15:53, 18 March 2013 (UTC)

User:Glrx, may I suggest that you read the posts between Arbitrary Section Break 3 and Arbitrary Section Break 7? Here you will see that is acknowledged by those involved with preparing IEEE 1459 that the standard has an error which will be fixed in the next edition (after all, it is clear from the math that the negative must exist - I do not believe anyone is actually doubting that). Given that, do you really feel that Wikipedia has a duty to help perpetuate the error? JohnJuliusFeinstein (talk) 16:18, 18 March 2013 (UTC)

IEEE 1459 says power flows from a source to a load. If you see a minus sign on your power factor meter, it means you've got the leads hooked up wrong, or you guessed wrong about the direction of power flow. Anyway, we have no credible sources that say the IEEE 1459 committee thinks this is unclear, all we have is OR from an account claiming to be someone on the committee. In this case, Wikipedia is not perpetuating the error, since it's not an error. Hmm, I've got an Ion 7300 here, I wonder what it does if I interchange dot and non-dot terminals on the CT circuit. --Wtshymanski (talk) 17:40, 18 March 2013 (UTC)

Mr Shymanski, I do hope that you are not seriously attempting to cast doubt on Sandy McEachern's identity? Here is a recent IEEE newsletter which confirms (page 17) his roles with IEEE, here is his CV from his own company's website, and the draft paper which he placed on that website, using your name as the reference, provides a convincing link between WP user AMcEachern and Alex McEachern, Founder, President, and Chief Technologist of Power Standards Lab. Please avoid using disingenuous tactics in an attempt to smear user AMcEachern. JohnJuliusFeinstein (talk) 19:11, 18 March 2013 (UTC)

When I was just starting out on my first real engineering employer, I was told something that I will never forget. Everybody is wrong sometime, but the wise engineer gets really happy when someone proves him to be wrong. This is a form of positive feedback that makes your mental model of the world closer to the actual technical details of the world.

Alas, the way this started makes that pretty much impossible for Wtshymanski to do. As he has done so often with so many people, he made it crystal clear that as far as he was concerned the only reason I believed in this mythical negative power factor was because I am a really, really bad engineer. He really was sarcastic and mocking, going so far as to create a special user page highlighting how silly and stupid I was being. So one can understand his reluctance to admit error. I think that the following applies here:

"The most hostile group was the one with high but unstable self esteem. These people think well of themselves in general, but their self-esteem fluctuates. They are especially prone to react defensively to ego threats, and they are also more prone to hostility, anger and aggression than other people."

"Hostile people do not have low self esteem; on the contrary, they think highly of themselves, But their favorable view of themselves is not held with total conviction, and it goes up and down in response to daily events. [He] has a chip on his shoulder because he thinks you might want to deflate his favorable self image."

--Roy F. Baumeister, Evil: Inside Human Violence and Cruelty Page 149

Always remember the First Rule of Holes: when you find yourself in one, quit digging. --Guy Macon (talk) 22:25, 18 March 2013 (UTC)

I do not know if anyone is keeping score: but this is the third article in recent times that has had to be protected because of Wtshymanski's constant edit warring. (Counting only the ones I am aware of.) I B Wright (talk) 16:06, 19 March 2013 (UTC)

Arbitrary Section Break 8

I am grateful for the progress that has been made on this topic, and for the kindness and respect that many Wikipedia users have shown to me. A few minor clarifications:

• I am, in fact, Alex McEachern as well as Wikipedia user AMcEachern. To help anyone who has any doubts, I have added "Active participant in Wikipedia power factor discussion" to my home page at http://Alex.McEachern.com. It's right at the very bottom.

• About IEEE 1459:

• There is no confusion in IEEE 1459 about negative power factor. There is one confusing statement that says, effectively, that power always flows from the source to the load. Editor Shymanski extended that statement to form his idea that power is always positive, and then extended that idea to conclude that power factor is always positive. But it is not an IEEE position that power factor is always positive.
• Figure 1 in IEEE 1459 clearly shows that power can be either positive or negative, and that implies that power factor can be either positive or negative.
• After the power definitions debate which I will moderate at the Summer 2013 IEEE Conference in Vancouver, where this topic will be thoroughly discussed, I expect that IEEE 1459 will be revised/updated/errated or corrected in some other way. But it is NOT my intent to modify IEEE 1459 to match the (incorrect, in my judgement) idea that power factor can be only positive. My judgement is that power factor can take any value between -1 and +1.

In general, I agree with the present state of the article. I do have a minor quibble with "A negative power factor occurs when the device which is normally the load starts to generate power which then flows back towards the device which is normally considered the generator..." To be precise, the words "starts to" are incorrect; the negative power factor is present whenever this condition applies, not just when it starts. If someone knows how to edit the article when it's locked, that might be a good correction to make. Thanks again to everyone! AMcEachern (talk) 22:50, 15 April 2013 (UTC)

I have personally confirmed that Wikipedia user AMcEachern is indeed Alex McEachern, fellow at IEEE, author of (draft) On Negative Power and Negative Power Factor in Alternating Current Power Systems: some corrections to IEEE Standard 1459-2010 , and owner of the alex.mceachern.com and powerstandards.com web sites. --Guy Macon (talk) 02:19, 16 April 2013 (UTC)

Wonderful. Now if we can only get user:AMcEachern to testify who is User:Guy Macon, we'll have a perfect authentication. --Wtshymanski (talk) 13:32, 16 April 2013 (UTC)

Actually, my identity can be confirmed. I can prove that I control the web pages, email addresses, telephone numbers and mailing address that I say I do, I have applied Template:User committed identity to my Wikipedia page, and I can provide a Notarized Identity Verification Form on request. A while back I had to confirm my identity and that I wrote a certain online document before testifying in a patent infringement case (Someone tried to patent the idea of using 60VAC/60VAC balanced AC power with the outlets normally used in the usual single-phase 120VAC (hot) / 0VAC (neutral) system. I testified that I had installed just such a system in a recording studio in West Hollywood many years earlier and that it was still being used.) Wtshymanski, might I remind you that it was you who claimed "anyway, we have no credible sources that say the IEEE 1459 committee thinks this is unclear, all we have is OR from an account claiming to be someone on the committee", thus triggering the above proof of identity? Please remember the First Rule of Holes: when you find yourself in one, quit digging. --Guy Macon (talk) 14:21, 16 April 2013 (UTC)

I fully agree that the words "starts to" in my original edit are ambiguous, and the final sentence of the first para of the lede should be changed to: "A negative power factor occurs when the device which is normally the load generates power which then flows back towards the device which is normally considered the generator." JohnJuliusFeinstein (talk) 01:18, 16 April 2013 (UTC)

Edit request

In the first sentence of the lede, delete the phrase:

"A negative power factor occurs when the device which is normally the load starts to generate power which then flows back towards the device which is normally considered the generator..."

Substitute

"A negative power factor occurs when the device which is normally the load generates power which then flows back towards the device which is normally considered the generator..."

Justification:

1. It is agreed above that the negative power factor occurs all the while power is being fed from the load to the generator and not just as the reverse feed starts.
2. None of the twelve citations supporting the point claim that the negative power factor only occurs at the start of the event.
3. The editor who inserted the phrase concedes that the words 'starts to' are ambiguous and that the lede should be changed in accordance with this request.

As for whether this page should be unprotected: this would not seem a good idea as Wtshymanski has made it clear that he will continue to misinterpret what the IEEE have to say on the subject of negative power factor ([1]). Unfortunately, Wtshymanski's claim that the IEEE have supported his view is not correct as documented (exhaustively) above including one of the contributors to that very document. The article is currently correct so no edit request is necessary on the disputed point of negative power factor. I B Wright (talk) 18:20, 16 April 2013 (UTC)

I agree that the above edit is uncontroversial and should be made. As for page protection, I think that the following edits say it all: [2][3] In these edits Wtshymanski flat out refused to follow our policies on consensus and edit warring. --Guy Macon (talk) 19:16, 16 April 2013 (UTC)

I had a go at reading #Negative Power Factor? above. Eight arbitrary breaks? Anyway. We did Power factor at college, Electrical Principles Level 3 - it was explained to us as the cosine of the phase angle between voltage and current; and it's possible for cosines to be negative, so Done, amended. Regarding the status of the prot: if you decide that it should be lifted, please file a request at WP:RFPP. --Redrose64 (talk) 20:06, 16 April 2013 (UTC)

• Support deletion of "starts to", but with reservations.

Phrases of "normally the load" and "normally considered the generator" should be edited, too. The noun phrases "nominal load" (or "named load") and nominal generator should be used instead. Normal ≠ nominal.

"A negative power factor occurs when the device which is the nominal load generates power that flows toward the device which is the nominal generator..."

Or simpler:

"A negative power factor occurs when the nominal load generates power that flows toward the nominal generator..."

Glrx (talk) 20:11, 16 April 2013 (UTC)

If you disagree with the edit that I made, please don't revert my talk page post. --Redrose64 (talk) 20:37, 16 April 2013 (UTC)

I don't disagree with your edit and I did not intentionally remove your talk page edit. I did not get an edit conflict warning when I edited the talk page. I had the talk page loaded before you made the change, and then proceeded to edit it and check the definition of nominal. I then clicked save, but the page did not load; instead I had a blank page displayed in my browser. I clicked back and then save again, and everything appeared normal.

I've seen other editors claim they inadvertently deleted an edit, and now I see a mechanism for that. My guess is WP throws away the lock instead of looking for an updated time on the submit.

Glrx (talk) 23:50, 16 April 2013 (UTC)

I don't disagree with your proposed change, but if you want it considered, you need to put it in the form of an edit request using the {{Edit protected}} template. You then need to state exactly what change you are proposing along with a justification (see my example above). If there is no previous discussion on the point, one will surely follow. An admin will then either make the edit or decline it. I B Wright (talk) 16:24, 30 April 2013 (UTC)

The cosine of 180 degrees is -1

Interestingly, Redrose64 has provided the basis for a nice little proof that power factor can be negative.

He said, "[Power factor is] the cosine of the phase angle between voltage and current". This is true, in fact it is often referred to as "cos Φ".

If the current flow reverses, its phase becomes 180 degrees to that which it was before the reversal.

The cosine of 180 degrees is -1   QED DieSwartzPunkt (talk) 14:44, 21 April 2013 (UTC)

Your answer is correct, but the definition "Power factor is the cosine of the phase angle between voltage and current" is not always true. It is only true in the specific case where the load is some combination of resistive and reactive (inductive or capacitive) and the voltage and current waveforms are sinusoidal with no distortion or harmonics. Try calculating the phase angle for figure 3 of [ http://www.ospmag.com/files/pdf/whitepaper/Power-Factor-and-Input.pdf ] or figure 3 of [ http://us.tdk-lambda.com/lp/ftp/other/pfc_switchmode_powersupplies.pdf ].

That being said, in the specific case of undistorted sinusoidal voltage and current waveforms, the cosine method does indeed show that when the voltage and current are 180 degrees out of phase, the power factor is negative. The power factor can also be negative in the case where the current waveform is highly distorted (see figure 3 again) -- simply reverse the phase of the current waveform -- but the only way to use the phase angle / cosine method in that case is to first perform a Fourier transform, calculate the cosine for each harmonic, and combine the results. This is, of course exactly what a modern power analyzer such as the Voltech PM1000 does. Look at [ http://www.ttid.co.uk/products-resale/voltech/voltech-pdfs/pm1000-brochure-tti.pdf ], which clearly states "Power Factor" -1.000 to +1.000". --Guy Macon (talk) 19:43, 30 April 2013 (UTC)

It's not necessary to have the specific case of 180° - all positive or negative angles between 90° (exclusive) and 270° (exclusive) have a negative cosine. So the voltage and current could be 91° out of phase, and the power factor is negative. --Redrose64 (talk) 20:31, 30 April 2013 (UTC)

Yes. Sorry for not making that clear. --Guy Macon (talk) 22:04, 30 April 2013 (UTC)

Though you are correct in the widely employed usage of the term 'power factor', it is not correct in the strictly accurate definition. The term 'power factor' is strictly defined as the cosine of the phase angle between sinusoidal voltage and sinusoidal current. To cover the situation where the current waveform is not sinusoidal, the alternative term 'apparent power factor' was coined which addresses that it is not the proper fower factor and is defined as real power divided by apparent power (or Watts divided by Volt-Amps). However, having said that, most engineers will just call it 'power factor' because it just happens to also be ratio of the real power to the apparent power - it's just not defined that way. Many technical works, including those from highly authoratative sources, have abandoned the strictly correct former definition of 'power factor' for the latter in order to sweep the problem introduced by non sinusoidal currents firmly under the carpet. The article here is no exception, but as the cited references support the point, this has to be regarded as acceptable. I could cite references for the alternate definition, but they all predate the introduction of non sinusoidal power supplies as the problem had not yet arisen. Addressing both concepts in the article would only serve to confuse the readership anyway. 86.145.244.180 (talk) 14:52, 4 May 2013 (UTC)

That really depends on where you stand on the prescriptive vs. descriptive issue. See Dictionary#Prescriptive vs. descriptive, Linguistic prescription#Prescription and description and Linguistic description

Standards such as IEEE 1459 are prescriptive, but Wikipedia pages are, by design, descriptive and not prescriptive.

If Wikipedia had been available around the fourth century B.C., it would have reported the view that the Earth is flat as a fact and without qualification. And it would have reported the views of Eratosthenes (who correctly determined the earth's circumference in 240BC) either as controversial, or a fringe view. Similarly if available in Galileo's time, it would have reported the view that the sun goes round the earth as a fact, and Galileo's view would have been rejected as 'original research'. Of course, if there is a popularly held or notable view that the earth is flat, Wikipedia reports this view. But it does not report it as true. It reports only on what its adherents believe, the history of the view, and its notable or prominent adherents. Wikipedia is inherently a non-innovative reference work: it stifles creativity and free-thought. Which is a Good Thing.
— WP:FLAT

As for any references you might cite, even if the authors intended them to be prescriptive, if they predate the introduction of nonlinear loads and they predate IEEE 1459, they are no longer prescriptive because they are outdated. --Guy Macon (talk) 22:05, 4 May 2013 (UTC)

I'm not sure exactly what point 86.145.244.180 was trying to make but if the 21st century references define power factor as the ratio of real power to apparent power (as they seem to do) then that is what the article should state. I have noted that article does address the issue of "apparent power factor" with respect to non linear loads, but uses (what I presume) is an alternative term "harmonic power factor". I B Wright (talk) 15:55, 12 May 2013 (UTC)

Contributors here might like to note that this elongated discussion has given rise to a paper on negative power and negative power factor (so not a complete waste of time). The paper is entitled, "On Negative Power and Negative Power Factor in Alternating Current Power Systems". The paper acknowledges the input from all the contributors here though is only able to name two of them (the rest of us being unknown). The paper in draft form can be found here. I B Wright (talk) 17:09, 5 June 2013 (UTC)

Very clear, well-written and sourced. Good job. I would suggest a couple of minor tweaks to that document:

First, "Wikipedia.org" isn't an actual website location. It is a common enough mistake that the servers at Wikimedia are programmed to redirect you to a real URL (http://www.wikipedia.org/) but even that is wrong -- the page you are reading is not on www.wikipedia.org but rather en.wikipedia.org (The English Wikipedia). The usual convention is to just say "Wikipedia" or possibly "en.wikipedia.org" (no capitalization).

Second, if you look at the title bar on the PDF document, it says it is "Microsoft Word - On Negative Power and Negative Power Factor Rev 2". This has always annoyed me; a document that is 'not in Microsoft Word format says that it is in the title text, just because Microsoft wants some free advertising. This is a metadata issue.

In general, before publishing anything in Word or PDF format, you should purge the metadata and put in information that will help the reader. In your metadata, in addition to the free advertising for Microsoft Word in the title, it has "PDF producer: Acrobat Distiller 10.1.5(Windows)" (information that is no use to the reader except as free advertising for Acrobat Distiller), the author is listed as "Alex" (should be the exact same spelling as the individual or organization used in the copyright notice), and the Subject and Keywords are blank. Putting appropriate text in those fields will help search engines to find and classify the document.

Here is some interesting advice from Adobe and from the national security agency about scrubbing metadata before publication:

http://www.nsa.gov/ia/_files/app/pdf_risks.pdf

http://ridethelightning.senseient.com/2010/08/adobes-advice-on-purging-pdf-documents-of-metadata.html

http://ridethelightning.senseient.com/2010/08/adobe-offers-more-helpful-metadata-scrubbing-tips.html

http://ridethelightning.senseient.com/2010/08/remove-metadata-from-acrobat-documents-as-part-of-ediscovery-readiness.html

http://ridethelightning.senseient.com/2010/07/metadata-scrubbing-are-lawyers-finally-getting-the-message.html

In my opinion, there should be a policy regarding metadata in the IEEE’s written data retention policies and procedures, and you might want to consider doing the same at Power Standards Lab.

Finally, as long as I have my "get every tiny detail right" engineer hat on, let us consider the directory and filename:

http://powerstandards.com/Shymanski/draft.pdf

This is just a personal preference of mine, but I like to see a somewhat more descriptive filename. It is really annoying when I have my IT hat on, someone asks me to recover a file, and it is one of 10,000 files with the exact same "draft.pdf" filename. I prefer something like NegativePowerFactorDraftV2.PDF. (Or Negative-Power-Factor-Draft-V2.PDF, Negative Power Factor Draft V2.PDF or Negative_Power_Factor_Draft_V2.PDF.) Windows has had long filenames since 1994.

Finally, since W.T. Shymanski has made it very clear that he thinks that you are dead wrong and insists that there is no such thing as negative power factor, he might not like having his name in the URL. Obviously http://powerstandards.com/GuyMacon/ is far superior... (just kidding. Something like http://powerstandards.com/IEEE_1459-2010_Corrections/ would be better). --Guy Macon (talk) 21:08, 5 June 2013 (UTC)

Edit request on 14 May 2013

Due to their very wide input voltage range, many power supplies with active PFC can automatically adjust to operate on AC power from about 100 V (Japan) to 240 V (Europe). That feature is particularly welcome in power supplies for laptops. 91.113.8.65 (talk) 15:48, 14 May 2013 (UTC)

Not done: please provide reliable sources that support the change you want to be made. --Redrose64 (talk) 20:49, 14 May 2013 (UTC)

Just as well. It is not the active power factor correction that achieves the wide voltage range. The power supply would still operate from the wide voltage range even if active (or any) PFC was not fitted. DieSwartzPunkt (talk) 11:52, 16 May 2013 (UTC)

It is a "free bonus" of the common method of APFC used in ATX PSUs, switchmode boost, that enable power to be drawn at all points on the AC cycle, assuming the APFC is designed to accept a maximum of 240V, and has sufficient boost capababilty to work as low as 100V. The standard with no or passive PFC is to use bridge rectification at 230V, voltage doubling at 115V. Ace of Risk (talk) 15:30, 16 May 2013 (UTC)

I don't think that that is unique to PFC power supplies. I haven't done a survey, but I believe that most switching power supplies have the ability to operate over a wide input range. --Guy Macon (talk) 19:27, 16 May 2013 (UTC)

Correct. I have a wide selection of such power supplies (you seem to get one with everything you buy these days). The earliest of these predate the requirements for PFC (and my PF meter confirms that they are not) but are specified to operate from 100-250 volts AC. Also, quite a number of modern PC power supplies still have a voltage switch (a shufty round the back of my 6 month old PC reveals such a switch on the power supply) so PFC has not granted it a wide voltage range. DieSwartzPunkt (talk) 16:32, 18 May 2013 (UTC)

A load is not a load if the averaged power factor is less than 1. It is a source, period. Cosine of 180 degree is in fact -1, this is true. But any passive reactive load cannot be a source and can only have a minimum reactive PF of 0.0, cosine(90)= 0.0, period. IFF, like an electric motor during regenerative breaking creates a PF of less than 0 up to a magnitude of -1.0 then it is called a source.

If you want to leave the definition as +1.0 to -1.0 simply put in parenthesis the word load and source, or more precisely Loading and Sourcing. Edit to... +1.0 (Loading) to -1.0 (Sourcing,)Done, over, complete, none confusing...User: I_B_GREEN, Green_Is_Now,CEO, Chief Efficiency Officer... — Preceding unsigned comment added by 161.84.227.12 (talk) 22:31, 6 June 2013 (UTC)

I think you must have meant a load is not a load if the power factor is less than 0. But I don't understand how this adds to the already very unnecessarily muddied discussion about active power factor correction and input voltage. SMPS do not rely upon power factor correction to operate on a wide input voltage range. For example, my laptop SMPS measures a PF of 0.5 yet operates between 100 - 240v. It appears the principal value of active PFC is to enable a greater power draw off from a mains circuit where the current carrying capacity of the circuit would otherwise be a limiting factor, or if you are power factor metered which is sometimes the case for large commercial power consumers. I suggest discussion of active power factor control has no place in the power factor article. The article should concentrate on what power factor means, how it is measured, and why it is important. Subjects such as power factor control or active power factor control could have their own space. Ramifications of APFC for SMPS should perhaps be reserved for the SMPS article where I am sure experts in SMPS will make sure the article is on target. Nick Hill (talk) 22:22, 9 June 2013 (UTC)

A load which is purely resistive (including those cases where X_L exactly balances X_C) will have a power factor of exactly 1. Any other load has a power factor less than 1. So you're saying that a 1 kW electric motor - which presents a substantial X_L - is a source? Hmmm. --Redrose64 (talk) 18:34, 7 June 2013 (UTC)

There is no need to argue about how to describe power factor. The IEEE has already figured it out, and it is slowly working its way to becoming a clarification of the existing standards. You can read it here:

http://powerstandards.com/Shymanski/draft.pdf

One key question to ask yourself it this: how do you describe a point in a circuit that has the current exactly 180 degrees out of phase with the voltage? If your preferred scheme cannot describe that or gives you the exact same answer as 0 degrees, you need a better system. --Guy Macon (talk) 22:11, 7 June 2013 (UTC)

I thought we got rid of the need for IEEE standards, now that Fluke meter manuals define our terms? One draft paper by an IEEE member does not make it the opinion of IEEE. ( recall some tsimmis a few years back by some lonely member publishing ...quite original...views on system netural grounding in a couple of papers. Didn't change the IEEE's "opinion", though, insofar as a collection of committees can be said to have a consistent "opinion" on anything.) There's a standards process, though why would anyone bother as long as we can consult some random WIki editor's toolbox for the gospel. Should have had their conference by now...I no longer subscribe to the "proceedings" but I expect the results will be on the Web by and by. --Wtshymanski (talk) 16:51, 8 June 2013 (UTC)

Wtshymanski, you have been warned about behavior such as the above.

On 19:11, 18 March 2013, JohnJuliusFeinstein wrote

"Mr Shymanski, I do hope that you are not seriously attempting to cast doubt on Sandy McEachern's identity? Here is a recent IEEE newsletter which confirms (page 17) his roles with IEEE, here is his CV from his own company's website, and the draft paper which he placed on that website, using your name as the reference, provides a convincing link between WP user AMcEachern and Alex McEachern, Founder, President, and Chief Technologist of Power Standards Lab. Please avoid using disingenuous tactics in an attempt to smear user AMcEachern."[4]

On 02:19, 16 April 2013‎, I (Guy Macon) wrote:

"I have personally confirmed that Wikipedia user AMcEachern is indeed Alex McEachern, fellow at IEEE, author of (draft) Some corrections to IEEE Standard 1459-2010, and owner of the alex.mceachern.com and powerstandards.com web sites."[5]

And at 22:50, 15 April 2013 (UTC) AMcEachern wrote

"I am, in fact, Alex McEachern as well as Wikipedia user AMcEachern. To help anyone who has any doubts, I have added 'Active participant in Wikipedia power factor discussion' to my home page at http://Alex.McEachern.com. It's right at the very bottom."[6]

After the above, for you to call him "some random WIki editor" and "some lonely IEEE member" is inappropriate behavior, even for you. Wikipedia user AMcEachern is indeed Alex McEachern, and Alex McEachern is not just an IEEE member, but rather is an IEEE Fellow (awarded for "contributions to power quality measurement"), and is the co-author of IEEE 519, IEEE 1159, SEMI F47, IEC 61000-4-30, IEC 61000-4-34, IEC 61000-4-11 and, most notably for the purposes of this discussion, co-author of IEEE 1459, which you kept citing on this very page ("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"[7]) back before the author of 1459 told you

"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 [incorrect, with my apologies] 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? "[8]

and

"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 Wikipedia should not deprive its readers of the fact that authorities disagree?"[9]

He is also the author of the Handbook of Power Signatures (generally considered to be the definitive reference on the subject) author of the Electric Power Measurements chapter of the Encyclopedia of Electrical and Electronics Engineering, chairman of the International Electrotechnical Commission (IEC) TC77A Working Group 9, which sets the standards for power quality instruments. He is also the former Chairman of IEEE 1159.1 and a voting member of the IEEE Standards Coordination Committee on Power Quality. And he holds 30 U.S. patents in the area.

For you, knowing all of the above, to imply that he is some random Wikipedia editor or some random IEEE member is tendentious, disruptive, and an unacceptable slur. Don't do it again or there will be consequences. --Guy Macon (talk) 19:59, 8 June 2013 (UTC)

This is what I get for trying to be subtle. For "some random editor", read "some random editor who owns a Fluke model mumblety-mumble power meter", if that clarifies it for you. I don't doubt (nor much care about) user AMcEachern's identity and the above wasn't about him. As for me, I am some random IEEE member, getting more random each time I log onto Wikipedia. If Mr. McEachern couldn't get the standard to read clearly after the last few revisions, why would anyone expect Wikipedia to get it right? We're lucky Randy from Boise hasn't equated "power factor" with "efficiency", citing something he saw last year on Discovery Channel as a reference. --Wtshymanski (talk) 17:12, 10 June 2013 (UTC)

Riiiiiiiight. when you wrote "One draft paper by an IEEE member does not make it the opinion of IEEE" you were talking about me, not the only person here who has written an IEEE draft paper. I just got in a shipment of a metric ton of WP:AGF, so I will take you at your word. (Drat! Almost out of AGF again! Better re-order...)

None of this, of course, changes that fact that said draft paper contains multiple citations to reliable sources establishing that negative power factor does exist, and you have provided exactly zero citations other than a self-contradictory IEEE document -- and the author clearly explained which of the two contradictory statements in that document is in error (the one you keep citing) -- supporting your claim that negative power factor does not exist. --Guy Macon (talk) 18:38, 10 June 2013 (UTC)

It was you (Macon) who quoted his Fluke manual as being evidence that negative power factor is not just an indication you've hooked up the instrument wrong. Mind you, when I quoted my Fluke manual and showed that a different instrument did not display negative power factor, I was brushed off. I am unimpressed by this style of argument. Since the fringe appears to contain a substantial number of IEEE standards contributors who in the last several revisions of IEEE 1459 did not feel it was useful and necessary to explicitly standardize the definition of negative power factor, I'm comfortable in that fringe. --Wtshymanski (talk) 15:04, 12 June 2013 (UTC)

Two ref expansions requested

1. replace ref http://www.iec.ch/zone/si/si_elecmag.htm with {{cite web |title=SI Units - Electricity and Magnetism |publisher=International Electrotechnical Commission |url=http://www.iec.ch/zone/si/si_elecmag.htm |archiveurl=http://web.archive.org/web/20071211234311/http://www.iec.ch/zone/si/si_elecmag.htm#si_epo |archivedate=2007-12-11 |accessdate=2013-06-14}}
2. replace ref [http://powerelectronics.com/mag/power_boosting_power_supply/ "Comparison between passive and active PFC solutions for a 250-W ATX application."] with {{cite web|last=Davis |first=Sam |url=http://powerelectronics.com/mag/power_boosting_power_supply/ |title=Comparison between passive and active PFC solutions for a 250-W ATX application. |publisher=Powerelectronics.com |date=February 1, 2005 |accessdate=2013-06-16}}

--Lexein (talk) 00:21, 16 June 2013 (UTC)

Nothing is lost or altered, all information added is neutral, so Done --Redrose64 (talk) 09:28, 16 June 2013 (UTC)