Talk:Power factor

what is the approx value of power factor which is maintain by factory

a approx value of power factor which is acceptable in no energy losses — Preceding unsigned comment added by 115.248.112.54 (talk) 13:33, 24 October 2017

Problems with first two plot figures

On the currently-first plot figure, the caption includes the statement "The blue line shows all the power is stored temporarily in the load during the first quarter cycle and returned to the grid during the second quarter cycle,"

This statement doesn't seem to make sense.

First, I'm pretty sure those "quarter"s should be "half"s, referring to the feature that the dark blue (instantaneous) Power curve is positive in the first half-cycle, and negative in the second half-cycle.

Next, Power is rate-of-flow of energy (Energy/second) and is not something that can be "stored". What can be stored in the load is Energy. The negative portions of the blue Power curve mean negative flow-rate-of-energy, indicating the direction of (positive) energy flow is from load to grid.

So I think the statement would be better as:

The dark blue "Power" curve shows that, during the first half cycle, energy flows from grid to load. Then during the second half cycle, energy, that was stored in the load, flows back to the grid.

There is a similar problem with the wording of the caption for the second figure. Gwideman (talk) 18:35, 3 November 2020 (UTC)

The phrases "stored power" (instead of "stored energy") and "absorbed power" (instead of "absorbed energy") are unfortunately used all the time! Just like "current flow" (which is redundant, instead of "charge flow"), "flow of current" (instead of "flow of charge"), "power flow" (which is redundant, instead of "energy flow"), "flow of power" (instead of "flow of energy"), "AC voltage" (which is misleading, instead of just "AV" or "alternating voltage), "conventional current flows from positive to negative" (which isn't always true, for example inside a source that is supplying energy, or inside an inductor that is releasing energy from its magnetic field), "to charge a capacitor" (which is misleading, instead of "to charge the capacitor plates"), "to charge a battery" (which is misleading, instead of "to energize a battery"), "electromotive force (EMF)" (which is misleading because it is a voltage, not a force), and "magnetomotive force (MMF)" (which is misleading because it is a current, not a force), they're misleading/wrong/redundant. --Alej27 (talk) 05:38, 4 November 2020 (UTC)

Well I'm not sure if you're saying that these misnomers are so common we should just accept them, or if Wikipedia should lead the charge to clean up technical language. I would lean toward the latter, though the most important criterion is for articles to be understandable to the largest number of readers. Almost anyone reading about "power" should understand that it refers to the time rate of energy flow, so introducing the proper term shouldn't have made it any more difficult to understand. However it would probably be best if at some point in the lede it specifically said that at least in passing. I'll let someone else edit the lede, but I just wanted to address what was a valid concern raised about the caption, but didn't look for every such possible correction where these misnomers are employed and will leave that for others. Interferometrist (talk) 14:51, 4 November 2020 (UTC)

I meant the latter: I'd love if Wikipedia promoted correct use of technical language. For the future reader, I'll explain why the phrases in my previous reply are misleading/wrong/redundant.

* Electromotive force (EMF) and magnetomotive force (MMF) are not forces. In physics, force is defined rigorously, and EMF and MMF aren't forces in this sense. EMF is a type of voltage, measured in volts; MMF is somewhat a type of current, measured in ampere-turns; force is measured in newtons. The textbook University Physics with Modern Physics, volume 2 (12th edition) by Young, Freedman, Sears, and Zemansky, makes this observation on page 857: “The influence that makes current flow from lower to higher potential is called electromotive force (abbreviated emf and pronounced "ee-em-eff"). This is a poor term because emf is not a force but an energy-per-unit-charge quantity, like potential.”

* Conventional current doesn't always flow from positive to negative, or equivalently, real current doesn't always flow from negative to positive. It's common to say that (conventional) current flows from positive to negative. But that's in general not true, even if we're talking about basic devices. That phrase is incomplete because they're not specifying in which device conventional current flows from positive to negative. For example, in a battery supplying energy, conventional current flows from negative to positive. In an inductor supplying energy previously stored in its magnetic field, conventional current flows negative to positive. I showed/proved this with GIFs and explained in more details in this answer on Quora (I hope that just by sharing that link, this reply isn't considered as self-promotion or spam.)

* Flow of current and current flow are redundant phrases; we should say flow of charge and charge flow. To support my point, I'll quote page 571 of the textbook College Physics, volume 2 (8th edition) by Raymond Serway, Chris Vuille, and Jerry Faughn, in which they say: “The phrases flow of current and current flow are commonly used, but here the word flow is redundant because current is already defined as a flow (of charge). Avoid this construction!”

* Flow of power and power flow are redundant phrases; we should say flow of energy and energy flow. For the same reason as why flow of current is redundant, flow of power is too. Both instantaneous current and instantaneous power are defined as rates, and rates don't flow. Now, many electric power engineers will disagree with me on this, probably because in one-line diagrams (whether in power systems analysis or in distribution systems design) used in power flow studies (also known as load flow studies), it is common to show the direction of flow of active power and reactive power (the software ETAP is one example), so it indeed looks like active power and reactive power flow throughout the system, but this is redundant. First of all, what is active power and reactive power? Active power is another name for average power, so, instead of saying active power flows from this bus to this other bus, we should say, on average, energy flows from this bus to this other bus. Regarding reactive power, this is a little trickier, so I won't address it in this reply. You can read this answer on Quora that explains why the previous phrases are redundant.

* A device doesn't consume or absorb power, its power is the average rate at which it is using or delivering energy, respectively (I say “average” because power usually means the active/real/average power).

* Batteries are not charged, they're energized, assuming to charge means to gain/lose net electric charge. In this video (https://www.youtube .com/watch?v=cPQbkTkGsnI) (join the link), a physicist named Nick Lucid criticizes the phrase “to charge a battery”. It is misleading because the battery doesn’t lose or gain a net charge when it is used or recharged, it only loses or gains energy. He suggests another phrase: “to energize a battery”.

* Capacitors are not charged, but their plates are. In this answer on Stack Exchange, a person (maybe an electrical or electronics engineer) named Phil Frost, at around the fourth paragraph, criticizes the phrase “the charge of a capacitor” or “to charge a capacitor”. It is misleading because a “charged” capacitor as a whole has no net charge, because the plates have equal but opposite charge. What is true, is that the individual plates indeed store charge. So we should use another phrase: “the charge of capacitor plates” or “to charge the capacitor plates”. Nick Lucid agrees with this fact (https://www.youtube .com/watch?v=cPQbkTkGsnI&lc=UgyejVM0i19bF_2ufWR4AaABAg).

* AC voltage means alternating current voltage, which is non-sense; we should say AV (alternating voltage). It's common to say “this outlet is 120 V AC”. I understand this phrase, but it is redundant. If we substitute “AC" for what it stands for, we get “this outlet is 120 V alternating current”. Well, not necessarily the current is alternating; for example if you plug in a charger (or rather, energizer?), the current won't be alternating direction, so we shouldn't call it AC, however the voltage is still alternating. So we should say “this outlet is 120 V AV”, or simply “this outlet is 120 AV”.

There're other misnomers, like calling the AC-DC adapter of a phone or laptop charger (energizer?) as a transformer. It is wrong because the adapter not only contains a transformer, but also a bridge diode rectifier, capacitors for filtering, and a voltage regulator. Anyways, they should be fixed. --Alej27 (talk) 01:30, 5 November 2020 (UTC)

Look, that's all very interesting but has to do with linguistics and I cannot agree on changing the terminology in this (or other) page for the reasons given. Redundancy is common in language and shouldn't matter when it couldn't possibly be misunderstood by the reader. For instance, "AC current" is obviously redundant but can mean only one thing. And AC voltage is equally unambiguous unless you don't know that alternating current and voltage almost always go together. Saying the "wind blows" is equally redundant, you should say the "air blows" but this would never be misunderstood by anyone who knows that wind involves the blowing of air. The original objection, which I corrected, had to do with using the WRONG word (power instead of energy) in a generic sentence, but terms which are unambiguous and don't cause confusion needn't be changed (especially when it involves, for instance, two different terms for alternating voltage/current).

But this is an interesting list, and you are free to create a new page called "Physics terms which are misnomers" or whatever, and you already have enough citations for it. Good luck! Interferometrist (talk) 19:23, 5 November 2020 (UTC)

I agree with Interferometrist. Articles should use common language constructs. Constant314 (talk) 19:26, 5 November 2020 (UTC)

This is almost pure pedantry, and much is incorrect.

Current is not a flow a charge. It is the rate of flow of charge (and is defined as such), to the point that one ampere is defined as the flow of one coulomb per second.

Flow of current or current flow is the accepted terminology to describe electrical charge flowing from one place another (specifically quantising the rate of that flow).

Similarly: power is not a flow of energy but the rate of flow of energy (and is defined as such), to the point that one watt is defined as the flow of one joule per second.

Similarly: Flow of power is the accepted terminology to describe any form of energy flowing from one place another (specifically quantising the rate of that flow).

MMF and EMF may not be forces in the mechanical sense per se, but they are magnetic and electrical forces respectively inasmuch as they force something to move from one place to another (in the latter case charge).

Electron flow always flows from a more negative place to a more positive place if there is no EMF forcing it to do otherwise. Conventional current flow is only positive to negative because Andre Marie-Ampere arbitrarily decided it should be so (the electron being unknown at the time).

Capacitors' plates are not charged. If you have seen a demonstration of a charged Leyden jar being dismantled and all the parts handled by the earthed demonstrator and then reassembled. The fact that the rebuilt jar can then be be discharged is clear evidence that the plates do not store the charge. Pedantically: the plates do store a very small charge but it is insignificant.

Capacitors are charged in that they are capable of holding a charge. Capacitance is defined as 'the ability of a body to hold an electrical charge'.

Batteries are similarly charged because they too will hold a charge (even though internally they convert the energy contained in that charge to chemical energy). Lithium-ion batteries behave almost exactly like a capacitor subject to some limitations. Indeed, over their useful charge range they behave more like capacitors than some real capacitors do.

AC volts and AC current, and their DC counterparts, are standard nomenclature and universally understood (and even Thomas Edison and George Westinghouse used the terms to differentiate their respective electrical systems). Pedantically, it is not strictly correct, but encyclopaedias are written by what is universally understood not on what is pedantically correct. Further the terminology is simplicity itself to source. Almost any multi-meter is marked 'DCV', 'ACV', 'DCA' and (if you have a posh meter) ACA. 86.142.79.215 (talk) 18:34, 2 December 2020 (UTC)

Shouldn't we clarify that power factor is usually never expressed as a negative number?

I understand why power factor can be negative. Just like why average/real/active power can be negative. However, we don't usually say "this generator absorbs -20 kW" but instead "this generator supplies +20 kW". Similarly, we don't usually say the power factor of a generator is negative, even though under normal circumstantes its absorbed active power is negative (i.e. its generated active power is positive), which implies PF < 0 since PF = P/S where S > 0. --Alej27 (talk) 16:31, 4 November 2020 (UTC)

Listen this issue was already debated, extensively (to the point I never read most of it!) on an archived talk page here: [[1]] - Interferometrist (talk) 19:33, 5 November 2020 (UTC)

Ups, I didn't know about that long discussion. --Alej27 (talk) 19:42, 5 November 2020 (UTC)

Whilst what you say is entirely correct for an electrical device that either exclusively generates power or absorbs power, you need to consider situations where power can either be absorbed or generated. The obvious example of this is a consumer who has installed solar cells. At night, such a consumer absorbs power from the grid which is usually considered positive power consumption (and the electricity meter records this positive power as an increasing display of energy consumption). However: during a sunny summer's day, the solar cells may well generate more power than the consumer is actually using. This surplus power is fed back to the grid and is considered to be negative power (in that it flows the other way). So much so that the electric meter now logs this negative power by running backwards. That is: the meter records this negative power with a decrease of recorded energy supplied. 86.142.79.215 (talk) 12:09, 3 December 2020 (UTC)

Specifying the circuits being discussed are LTI (of constant parameters) is not a leap too far

Anonymous user of IP 86.129.19.88 reverted my edit to this version. Their reason:

"This concept is a leap to far for an article of this nature. It only serves to obfuscate the issue being discussed. Simplicity is always better."

In my edit, I clarified that it is linear time-invariant circuits (and not any linear circuit) that don't change the shape of applied volage in the resulting current. In other words, I fixed a mistake. There are linear circuits that produce harmonics: linear time-variant circuits. However, the user reverted my edit, making the article wrong again.

In my edit, I didn't go into much details of what was a time-invariant circuit. Instead, I just changed the words "linear" for "linear time-invariant", and I even added a short example of such a circuit: a circuit whose R, L and C are constants.

"It only serves to obfuscate the issue being discussed." // I don't think so. It serves to clarify what is being discussed: LTI circuits, not just any linear circuit.

"Simplicity is always better." // Yes, simplicity is better, as long as it is correct, which was not the case. So that's why I corrected the article.

Don't you prefer to have a specific but correct explanation than a shorter but wrong explanation? --Alej27 (talk) 20:17, 20 June 2021 (UTC)

In ordinary parlance, a resistor, capacitor, or inductor (or a linear amplifier) without further qualification is considered linear and time-invariant EVEN THOUGH there is always SOME voltage or current that can overload or destroy it, but that doesn't change its basic character. A VARIABLE R/C/L is considered to be linear on the timescale of the signal even though it changes when someone turns the knob. Yes, if a 100Hz signal is processed by an LTI circuit while someone turns the knob on millisecond time scales then you get new frequencies, but that doesn't justify changing our normal way of speaking. If the R/C/L is dependent on voltage or current then it obviously isn't linear, but you have different names for such components. There is always non-ideal behaviour that needn't be pointed out when it isn't dominant. Otherwise we could never talk about a resistor or capacitor without specifying its stray inductance, leakage, temperature dependence etc. These are a higher level of detail that shouldn't be introduced into the basic explanations. Interferometrist (talk) 21:10, 2 July 2021 (UTC)

Here's the diff in dispute. Alej27, I've added a link to Linear time-invariant system to help readers through this terminology you've introduced. I think it is a reasonable assumption that electrical parameters for the R, L and C devices are constant so stating that qualification is unnecessary. ~Kvng (talk) 14:10, 5 July 2021 (UTC)

I think the current version as edited by Kvng is good. It doesn't say the R/L/C are constants (so I think it is in agreement with Interferometrist), but it also clarifies the wrong statement that linear circuits always produce sinusoidal outputs of same frequency to sinusoidal inputs (it's false, they don't, e.g. linear time-variant circuits). --Alej27 (talk) 17:26, 5 July 2021 (UTC)

Thinking back, long ago to my university lectures, it seems that in each class that the professor would say, once, near the beginning of the semester, that the math applied to linear time-invariant circuits. He did not elaborate. He was being rigorous, but not tedious. One time, I asked if a certain result always applied and the professor replied, “yes, for linear time-invariant circuits.” I suppose hearing it often enough drummed it into my consciousness. I think that is what we should do in this article. Mention it once, with a wiki-link, without elaboration and move on. Constant314 (talk) 18:06, 5 July 2021 (UTC)

@Constant314: So in section Linear time-invariant circuits we should say something like "Linear time-invariant circuits (referred to simply as linear circuits for the rest of this article), for example, circuits consisting of combinations of resistors, inductors and capacitors have a sinusoidal response to the sinusoidal line voltage"? That'd be a good idea, since in the current version of the article, loads are still called as linear even though they are actually linear time-invariant (e.g. the power triangle doesn't hold true for linear time-variant loads). --Alej27 (talk) 07:54, 21 July 2021 (UTC)←

Sure, put in that parenthetical remark if it helps. When you don't specify otherwise, time-invariance is almost always assumed. You have to go to a lot of trouble to make an actual physical system that is not time-invariant, and even further to find an actual use for it. And in cases when something is labelled non-time-variant (like the "examples" I removed from the to-be-deleted "time-variant" page), there isn't any clear distinction between saying that and saying that it's a non-linear system with two inputs. So I don't know about any "time-varying loads", but perhaps you're referring to a motor under differing back torque, in which case you could just as well call that torque an additional input in a nonlinear system. So although "time-invariant" is a useful and correct qualifier, it hardly ever needs to be pointed out when you just say "linear system" or linear component. Interferometrist (talk) 15:34, 21 July 2021 (UTC)

I'm good with that. Constant314 (talk) 20:40, 21 July 2021 (UTC)

Typos

Seems like every page ought to have a section for just typographical errors. Anyway, this "The power factor...or equivalently the angle by which the voltage" seems to be missing a word. It should be "...equivalently the sine of the angle...". The whole sentence seems unnecessarily long, though. I would suggest The power factor is the cosine of the angle θ ... Captain Puget (talk) 22:41, 19 November 2021 (UTC)

Go for it! You might as well fix the article as comment on it on the talk page, especially for stuff like this. --Wtshymanski (talk) 21:57, 22 November 2021 (UTC)

No. Because it is the same angle. It is still the phase angle between current and voltage whichever way around you express it. Why we actually need to express it the other way around is another matter. 86.188.36.150 (talk) 18:05, 6 December 2021 (UTC)

not understandable

This article doesn't make understandable what this power factor means or is supposed to be. It seems to indicate that "power" (whatever that means) somehow magically disappears because more current is being drawn from a supply than the device connected to the power supply receives.

In this case, I'm looking at a power meter connected to a Dell R320 server with 2x350W PSUs connected to a 230V supply, and the power meter says the power factor is 36 while the server is turned off. What the hell is that supposed to tell me? This article doesn't answer the question at all.