Talk:Coupling coefficient

Resonant inductive coupling

I have removed the link to resonant inductive coupling. Firstly, it is describing the coupling between two inductances. That is precisely what the inductance article is describing at Inductance#Coupled inductors and mutual inductance so we don't need two links. Secondly, the resonant inductive coupling page completely fails to explain what it does mean by couplng coefficient. Nowhere is there a definition or a usable formula. A lot of stuff about how it's misunderstood, but it never succeeds in getting to what it should have opened with – what it is, rather than what it is not. Thirdly, it gives the range of k as 0 to 1. Sources (and the inductance article) give the range as ±1. SpinningSpark 18:33, 7 January 2017 (UTC)

As my proposal, I think that we should make the article of coupling coefficient and leakage flux. Although it is clear that it is expressed by the formula, it is necessary to mention that many people misunderstand that the coupling coefficient is the effective magnetic flux ratio. I found that there are mistakes in some descriptions. This is due to the fact that the definition of leakage flux in electromagnetism and the definition of leakage flux in magnetism are different. Do you recognize this fact? In some cases, the same technical term is used in different meanings in different fields of expertise. Leakage flux is a typical example of it. And electromagnetism and magnetism should not be confused. The link which presented by you has a description that confused both fields.118.236.168.22 (talk) 22:47, 7 January 2017 (UTC)

What I think we really need is an article here on this page covering coupling coefficient in general. Coupling coefficient can be defined in a general way, and is widely used in all sorts of transducers, not just electromechanical ones and transformers. As for your claims on its definition, let's see some reliable sources on the subject first and then write from that. That's the way it's done on Wikipedia. As for "necessary to mention that many people misunderstand", no it's not. We don't tell our readers what they are misunderstanding. We just give them the facts. See WP:NOTTEXTBOOK and WP:WEASEL for our policy on this. SpinningSpark 00:07, 8 January 2017 (UTC)

Well, I would like to ask if you think that this description is correct. At the link you indicated, it is said that the inductance ratio of the coupling coefficient is equal to the flux ratio. As for the formula,

σ_P = Φ_P^σ/Φ_M = L_P^σ/L_M

σ_S = Φ_S^σ'/Φ_M = L_S^σ'/L_M

But, it is common sense in the electromagnetism that the flux ratio dynamically fluctuats depending on the load condition. I can show several literature about it. According to his formula, if the inductance ratio is fixedly determined, the magnetic flux ratio is fixedly determined. So this formula is clearly wrong. I care very much about him because I do not want to hurt this editor's pride for peace.118.236.168.22 (talk) 02:53, 8 January 2017 (UTC)

Sources come first, and then the discussion. I am not seeing the claim you make of the inductance article, please provide an exact quote so I can find it. As for not hurting anyone's feelings, please read WP:OWN. Articles do not belong to anyone. SpinningSpark 16:59, 8 January 2017 (UTC)

If possible we would like to unify discussion here, so you should also refer to it together.

Talk:Leakage_inductance#The concept of "ratio of magnetic flux = inductance ratio" is incorrect

Maybe it will take some time for the conclusion to come out. It is even better if you can help this discussion with your knowledge.　And I have to reflect on my short temper.121.2.184.184 (talk) 22:46, 8 January 2017 (UTC)

Coupling factor and coupling coefficient

According to the IEC 60050 (Publication date: 1990-10) Section 131-12 IEV 131-12-41, there is the following relevance between the coupling factor and the coupling coefficient.

${\text{Coupling factor}}=\left|{\text{Coupling coefficient}}\right|$

--121.2.183.152 (talk) 05:32, 15 January 2017 (UTC)

Your linked source says no such thing. SpinningSpark 09:43, 15 January 2017 (UTC)

There is written "where Lii and Ljj are the self-inductances of the elements and Lij their mutual inductance.", and the Lij is the absolute value.--121.2.183.152 (talk) 14:29, 15 January 2017 (UTC)

and are any of those things "coupling cefficient". Sorry, it just doesn't say that. It doesn't say what the range is either; consider what the square root produces. Now the authors might have meant to write magnitude of the whole expression, but they haven't. A minority of sources give −1 < k < 1 eg this book SpinningSpark 17:23, 15 January 2017 (UTC)

As a result of careful consideration, the coupling coefficient was derived from Electromagnetism and the coupling factor was derived from Magnetism. So they shouldn't mixed and should be independent.--123.198.124.180 (talk) 22:53, 16 January 2017 (UTC)

So these values ideally coincide with each other, but in general they do not match within the range of error.--123.198.124.180 (talk) 22:59, 16 January 2017 (UTC)

I get it that you want to create links to the Leakage inductance article, but you are breaking all the rules of disambiguation pages. Please read MOS:DAB before doing anything else. The leakage inductance page has exactly the same definition as the inductance page. They are the same subject and should have only one link on the page. Secondly, we do not hide the true title of target articles behind pipes on disambiguation pages. I also think you should really create an account if you are going to take part in discussions. It is difficult to communicate with you properly when your IP address keeps changing. SpinningSpark 23:16, 16 January 2017 (UTC)

In Magnetism the coupling factor is the value obtained as a result of prediction of permeance. On the other hand, the coupling coefficient in Electromagnetism is the theoretical value obtained from mutual inductance as results. So, to be precise,

${\text{Coupling factor}}\cong \left|{\text{Coupling coefficient}}\right|$ --123.198.124.180 (talk) 23:43, 16 January 2017 (UTC)

First of all, can you provide a source that says that? If you can, then point to an article on Wikipedia that is following that source. Otherwise it simply does not belong on the disambiguation page. The leakage inductance article simply does not say anything different from the inductance article. And how many times do I need to tell you that we don't pipe links on disambiguation pages? SpinningSpark 00:12, 17 January 2017 (UTC)

The origin of the coupling factor have already been shown, where permeance is written. Obviously it will be different from that of Electromagnetism.--123.198.124.180 (talk) 00:24, 17 January 2017 (UTC)

Where has permeance been written? What I am asking for is a reliable source that says these two factors are different concepts. SpinningSpark 00:29, 17 January 2017 (UTC)

Please show IEV 131-12-41. The permeance is written there.--123.198.124.180 (talk) 01:09, 17 January 2017 (UTC)

Based on the definitions in the cited IEC doc and book, I agree that the factor is the absolute value of the coefficient. If there are further differences, making this relationship approximate based on whether its measured or theoretical, I'd definitely need sources to verify. I can see that we might want to link the relevant sections in both Inductance and Leakage inductance, but I'm at a loss to understand what is meant there by Magnetic versus Electromagnetic; does it mean that the electromagnetic one considers direction of current flow, and the other does not? Sources, please. Dicklyon (talk) 01:00, 17 January 2017 (UTC)

The coupling factor is important for the Mmagnetism person. On the other hand, the coupling coefficient is important for Electromagnetism person. On the other (third) hand, for electronics engineers these differences do not so large matter. It is enough to use the result.--123.198.124.180 (talk) 01:17, 17 January 2017 (UTC)

Ah, I found a book that talks about mutual permeance being nice because it doesn't depend on numbers of turns; is that the distinction? I don't think invoking different kinds of persons can explain this. Dicklyon (talk) 01:20, 17 January 2017 (UTC)

Probably because every person's positions are different, I think that conclusion will not come out soon. By the way, I am interested in the description of those book.--123.198.124.180 (talk) 01:25, 17 January 2017 (UTC)

It just a snippet I saw in book search; see [1]. Dicklyon (talk) 03:18, 17 January 2017 (UTC)

Dicklyon, there are numerous books that define coupling coefficient as always positive.[2][3][4][5]. Sources allowing it to be negative are very much the minority. This paper was one of the few I found. They needed to take into account the sign because they had deliberately printed a planar secondary with the opposite handedness of the primary to achieve a negative coefficient. Most books just say it is always positive. It doesn't amount to a different thing, sources are using factor and coefficient synonymously regardless of whether they think it is + only or + and -. SpinningSpark 02:06, 17 January 2017 (UTC)

Tangential discussion

Seems to me that for Network_analysis_(electrical_circuits), it is usual to give the voltages and currents symbols before knowing the actual sign. For example, when working with SPICE, one can go through a schematic and write down the appropriate SPICE input data set, without knowing the signs. One could, though predefine coupling as positive, and take that into account. The latter is likely more work. In terms of book descriptions, other than ones that write the text after the figures, it should always be possible to define them as positive. But the generality of delaying the sign until later, often enough seems useful. Gah4 (talk) 02:23, 17 January 2017 (UTC) No, that is not what is happening, the sources are not just assuming positive, they are explicitly stating 0 ≤ k < 1 SpinningSpark 02:39, 17 January 2017 (UTC) Well, OK, but you have to assume positive before you say that, or the other way around. As a more obvious example, it is usual to give resistors positive values, and assume that the current and voltage are appropriately defined. That is a little more obvious, as resistors often get used in negative exponentials, where you don't want the wrong sign. But with some signs for voltage and current, one will find that the R value is negative. Gah4 (talk) 03:08, 17 January 2017 (UTC) More specifically, in informal discussions you can give it a positive value. If you write down input data sets for a program like SPICE, you have to get all the signs right. In the latter case, you can define k as positive and assign the current/voltage polarities as appropriate, or give the voltages and currents signs, and determine the sign of k. Gah4 (talk) 03:23, 17 January 2017 (UTC) You should never get a negative value for a normal, passive resistor whatever convention you define for sign of voltages and currents. If you do, you have done something wrong. SpinningSpark 03:38, 17 January 2017 (UTC) This is obviously not true. If you use V=IR, and change the sign of one of V or I, and not both, the sign of R changes. I suspect, though, that people try harder to define V and I such that R is positive. The question, then, is how hard to they try for k? With digital voltmeters, it is usual to connect the meter and then determine the sign. In the analog meter days, it was usually to try to determine the sign first. Technology advances. Gah4 (talk) 04:13, 17 January 2017 (UTC)

Yes, I see your point. Most sources treat them as the same thing. Are they any that treat both, with the absolute value being the difference? If not, then I agree it would be a mistake to synthesize that from multiple sources. Dicklyon (talk) 03:21, 17 January 2017 (UTC)

So far I haven't found any. This is exactly the question I have been asking the IP editor. SpinningSpark 03:38, 17 January 2017 (UTC)

And the issue of whether the terminology distinguishes the signed, and unsigned quantity is not really relevant to the dab page. That can be taken care of in the linked article, if there is such a distinction. The big issue here is that the dab page is trying invent a new topic that is not supported by the linked articles, they both have the same description. So far, we have no support in sources either. But in any case, the first step is to get something that differentiates them in an article, not distort the dab page with links hidden behind pipes. SpinningSpark 10:41, 17 January 2017 (UTC)

Magnetostatics

I am not so sure what to say about the above discussion, but I do note that it is sometimes comparing electromagnetism to magnetism. Note that from Maxwell, changing electric fields produce magnetic fields, and changing magnetic fields produce electric fields. Magnetostatics is the study of non-changing magnetic fields, such that electric fields are not produced. Transformers are electromagnetic, though often enough the low frequency approximations can be used.

In many fields, there is use for a value that is the absolute value of another value, enough to give it a different name. We have speed and velocity for that reason. In the case of electromagnetic coupling, sometimes one doesn't need to worry about the sign, and other times one does. I don't know that there is enough reason to give them two different names, though. For example, when one is discussing electromagnetic interference (EMI), which can either be capacitive, inductive, though most likely both, the sign doesn't matter much. (On the other hand, twisted pair cables are designed to cancel out coupling by changing its sign at the appropriate interval.)

Seems to me that to resolve this, enough reference will be needed to make the statistical case that two terms are, or are not, used differently. For many articles, some subject is well enough known that every knows the meaning, but one still wants a good reference. In that case, one or two will do. That is not true here.

I notice that the coupling factor in Power_dividers_and_directional_couplers#Coupling_factor is 10 log of a power ratio. That is, its sign does not represent the sign of the coupling. In many cases in microwave electronics, it is easier to measure power than voltage and current. (Well, electric and magnetic fields.) As the fundaments physics of coupled electromagnetic fields isn't all that different between microwave circuits and transformer circuits, other than the frequency, I don't see a need for two different names. I suspect that some authors are using one term, and others the other term. Gah4 (talk) 01:53, 17 January 2017 (UTC)