Talk:Polarity (mutual inductance)

The derivative is important
Since the strict relationship is between the time derivative of the input current, and the output voltage, I think it would be better to talk about input current increasing into the dot. JohnAspinall (talk) 16:16, 27 August 2009 (UTC)

Agree - this article is only true in the case of sinusoidal ac, as it stands. IanOfNorwich (talk) 15:46, 1 March 2011 (UTC)


 * My understanding of transformers is that they also act as ordinary inductors, so that, with no load on the secondary, the current and voltage on the primary side would be 90° out of phase. So even with sine waves I still think you have to talk about the rate of change. I reworded part of it accordingly. I wonder if that “Sinusoidal AC” section is worthwhile keeping. Vadmium (talk, contribs) 05:38, 6 February 2012 (UTC).

Reference
Reference may be Standard IEC 60375, which however is under revision. Erik-pontus (talk) 17:16, 19 March 2011 (UTC)

The picture is confusing
Current always flows from '+' to '-'. Arconductor (talk) 06:29, 3 September 2011 (UTC)

Actually the current flows from - to +, not the other way around. Nonetheless the picture should still be corrected. 74.88.249.174 (talk) 20:08, 6 November 2011 (UTC)


 * Actually the + and − in the diagram would be references for measuring voltage. The arrows labelled I1 and I2 would be references for current. But the sign of these currents would depend on the application. Vadmium (talk, contribs) 05:38, 6 February 2012 (UTC).


 * In a DC sense, current is considered, by convention to flow from + to -. Introducing the concepts of + and - to AC circuits is confusing. DieSwartzPunkt (talk) 16:01, 7 May 2012 (UTC)

perpendicular inductors
what if the inductors are perpendicular? the voltage is NOT necessarily zero. — Preceding unsigned comment added by 67.1.73.197 (talk) 06:03, 5 April 2012 (UTC)


 * In an ideal world, the induced voltage would be zero. But we don't live in an ideal world so, in practice, you are right.  The induced voltage, though small, is not zero. DieSwartzPunkt (talk) 16:02, 7 May 2012 (UTC)

Ambiguity
Out of the four possible dot configurations, pairs of two are electrically identical in theory (as shown in the article already), however, they are not necessarily identical in practical use. I seem to remember that there was more to the two equivalent configurations than explained in the article. Sometimes (e.g. for safety reasons), it is important to know the "start" of coil, that is, which of the (two) leads on one side is the "inner" or the "outer" lead. As far as I remember, this is encoded in the dot convention as well, although right now I don't remember which way around. --Matthiaspaul (talk) 12:11, 18 April 2013 (UTC)


 * They are not equivalent if you consider interwinding capacitance. But you have to know the order of the windings on the core, and also know if there are bifilar windings. Gah4 (talk) 18:28, 7 November 2016 (UTC)

Dot end polarity is always + polarity
The diagram is in my view wrong. Dot end polarity is by convention always positive polarity!?
 * The diagram is quite correct! The dotted end of a winding does not indicate positive polarity, positive going polarity, increasing current or voltage. The dotted end of a winding indicates the same instantaneous polarity as another winding's dotted end. This convention only works with two dotted ends and indicates the relative parameter by association. There is nothing absolute about the marked end.
 * Since AC is almost always involved with transformers relative polarity becomes harder to express but you will find any decent transformer knowledgeable engineering text using the term same instantaneous polarity and only comparing like with like. This is expressing it as a snapshot in time. Texts stating currents against voltage, for relative polarity purposes, are just confused and don't understand the simple concept. Yes, currents will be the same instantaneous polarity and voltages will be the same instantaneous polarity from a transformer but an unloaded transformer can only match voltage polarity. Magnetizing current will be almost 90 degrees lagged in the primary of a transformer and yet the secondary voltage will be in phase with the primary voltage. You can't mix them for polarity definitions.
 * Another editor touched on something I found years back in my transformer manufacturing years. Coil winding machines only wind coils one direction. When the winder starts a winding he will mark the lead with tape, dot, tag, etc. When he finishes the first winding he will start the next winding, marking the start lead similarly. Testers can identify coils with a simple continuity test for a $10 meter but the relative polarity between windings is harder to identify. Further, the start end of a winding will be closest to the lamination core when assembled so the installer would use the dotted end as the neutral or lowest potential end of the circuit. Somewhere in history (I saw in in the 1970-80s) circuit designers reversed the connection concept and most, now use the dotted end for live, hot, highest potential in the circuit, saying it doesn't matter and it's easier to understand the consistency.
 * Please sign your edits with four tildes so that readers know the timestamp and who is making statements or questions. All this time reverting people's edits on this subject matter and you don't understand it? Many editors have attempted to correct your edits, on this, only to have given up and not participated anymore. 174.118.142.187 (talk) 23:29, 22 April 2013 (UTC)
 * Thank you for your valueable input which puts my assertion on ambiguity further up into much better words. You mentioned that the meaning of the dot might have been swapped or wisdom on its original meaning gone lost over the decades.
 * Unfortunately, I don't know the answer, but I know of a real-world example, where a transformer was used in an automotive application and without any apparent change the resulting assembly stopped working reliable at some point. When QA examined the problem, they found that there were no changes in the design or layout of the circuitry, nor were there any changes in the values of parts or their manufactures. Still, starting in the middle of a certain production run, their products no longer worked. All parts were the same, except for the transformers - well, sort of. The transformers looked identical and their part number and manufacturer was still the same as well, and within the limits of tolerances various lab tests on unsoldered transformers showed no apparent differences in their performance as well, still older samples of them worked in the design, whilst newer ones did not. When the manufacturer of these transformers was approached it turned out that these transformers were from a newer production run, and that the winding machine had changed so that the newer transformers were wound clock-wise, while the older ones were wound anti-clock-wise. The transformer's configuration was still "parallel", not "anti-parallel", and they were using the same leads and other stuff. The transformer and the data sheets had no markings, it was just indicated as a 1:n transformer. This was one of the events when I learned about the dot convention, however, so far I was unable to come up with a formal definition if the dot should mark the "input" or the "output". Most books on transformers don't mention the convention at all, and those which do (spanning over some 35 years) seem to use it in one way or the other without explaining it.
 * You also explained that in some applications it is important to know, which end of the winding will be closer to the core. This is exactly what I meant by safety reasons.
 * It is possible, that the meaning of dots has changed over the decades, or that their meaning on the real thing is reversed to the meaning in circuit diagrams, so that it can no longer be used reliable to indicate the start of a winding, if it ever could. But even if so, I think, the article should try to discuss this development. If nothing else it is historical interesting information. We just need to find sources...
 * --Matthiaspaul (talk) 01:23, 23 April 2013 (UTC)
 * Well, 187, you do seem to know whereof you speak of regarding polarity. I will ponder this + polarity further. This is anything big reassuring, I mean, the part asserting that + does not mean dot end.Cblambert (talk) 01:34, 23 April 2013 (UTC)
 * I spent most of my life building and then testing these beasts. In meterology relative polarity is very important. PTs must all match and CT must all match and match them or the metering doesn't work correctly. This applies to anything that needs to know power flow. Relays that watch HV lines need to know direction of power flow and have the same pickiness.
 * Some things that shouldn't be used in polarity definitions. Increasing current especially when we are talking about AC currents. Not related to polarity. Increasingly positive current could mean the AC current is increasing "up". Positive and negative should not really be used in AC unless discussing instantaneous values. AC uses RMS, power flow. Polarity is a nickname short form we all use in the field but it is not descriptive for an encyclopaedia. Relative needs to be used. I have heard a thousand definitions, verbally, about polarity and the only ones that work well are the ones that used the "time freeze snapshot" analogy by stating same instantaneous polarity. Think storage oscilloscope with both windings. I know differentiation is behind the real induction stuff but for good 'ole AC it works. I have a story about a 2MVA ground bank (yeah, zigzag) polarity testing using two 6 v lantern batteries. Discussing why it wasn't working we left the DC on too long and drew a 8-9" arc when we attempted to remove the connection. It was rated at 87% impedance. I learned about impedance first hand! 174.118.142.187 (talk) 02:53, 23 April 2013 (UTC)

This still does not explain why same dot polarity does not equate to same + polarity. Otherwise, showing + polarity on AC system is useless, misleading. Why do tests in fig. 3-21 p. 73 of Kothari reference's link http://books.google.ca/books?id=fR1rNJhBbmcC&pg=PA72&lpg=PA72&dq=dot+convention+polarity+of+transformer&source=bl&ots=JbPSAdgSl1&sig=QFFm_taBOowUXfqzrPq0HomP0bo&hl=en&sa=X&ei=bQJAUdLeJ9KCrQGK34GADQ&ved=0CE4Q6AEwBjgK#v=onepage&q=dot%20convention%20polarity%20of%20transformer&f=false equate dot polarity with + polarity? Why does article not show tests do put this issue to bed once and for all? Article diagram is still in my view questionable at best. Cblambert (talk) 07:02, 23 April 2013 (UTC)
 * I don't agree that:


 * ANSI/IEEE reference's definition of polarity is not valid for instrument transformer.
 * Positely-increasing instantaneous current in one winding's dot end does not induce positive polarity (+) voltage in other winding's dot end.
 * I just don't buy it without clarification.Cblambert (talk) 07:15, 23 April 2013 (UTC)
 * Quoting from Kothari test at above link:
 * ". . .The positive polarity of this induced emf in the primary is at the end to which the battery positive is connected (as per Lenz's law). The end of secondary which (simultaneously) acquires positive polarity (as determined by the dc voltmeter) is the similar polarity. The reverse happens when the switch is opened, i.e. the similar polarity end of the secondary is that which acquires negative polarity. . . ."
 * THE OLD DIAGRAM IS WRONG. DOT END POLARITY IS ALWAYS + POLARITY. THE NEW DIAGRAM WITH VOLTAGE EQUATIONS IS RIGHT. THE WORDING IN POLARITY IS RIGHT. LENZ'S LAW ALWAYS APPLIES.Cblambert (talk) 16:59, 23 April 2013 (UTC)
 * Again..., Transformers work on AC principals and unless you want to get into power flow in terms of a reference voltage and watt reading polarities (I don't for the reader's sake, It gets too abstract), you will have to define in terms of INSTANTANEOUS values. Again... "A frozen in time, snapshot". Until you can understand this necessary concept you should not be editing this article. It seems you don't understand these basic concepts, as explained several times and proposed edits are based on that. Placing math formulae in this article, as it does not help in any way for the reader to understand this simple concept, will be reverted. This is especially applicable for images with formulae in the graphics, contrary to WP:Manual of Style/Images. You have supplied no reference links and I do not have hours of time to guess what they are. Are you aware of the cite template tools? ~.174.118.142.187 (talk)  —Preceding undated comment added 19:28, 23 April 2013 (UTC)
 * The old image should not include + and - notation whether explaining what it means. The article needs to address all issues. I too don't have the time to argue certain things. You don't own this article so you don't have the right to say what anybody will be allowed to do. You don't need to patronize anyone. A formula is a formula whether or not it in body or in the image.Cblambert (talk) 00:59, 25 April 2013 (UTC)
 * Here is explanation for connection between +/- polarity and dot convention:
 * http://faculty.citadel.edu/potisuk/elec202/notes/xformer.pdf
 * So the answer to the original question, Is 'Dot end polarity is always + polarity'?, is that:
 * the answer has less to do with reconditions about elaborate power flows, as important as they may,
 * the answer has more to do with the dot end polarity is not always +ive but the dot convention is meaningless unless you also define the direction of currents and voltages of the mutual inductance circuit.
 * Note in explanation link how n = V1/V2 = I2/I1 = turns ratio
 * So the old diagram is wrong unless and until the article provides this explanation about meaning of +/- convention.
 * If the old diagram does not provides this explanation, the old diagram is wrong.Cblambert (talk) 01:58, 25 April 2013 (UTC)


 * "+" and "-" indicate absolute polarities of DC voltage or instantaneous values in AC theory. Dotted winding terminals indicate relative AC polarity.
 * AC power flow and current flow are not into or out of a dotted, a "-" or a "+" end of a winding. Power flow direction is into a winding given reference parameters. The same current flows through both ends of a winding. AC current is not positive or negative but alternating.
 * The original diagram is correctly labels and demonstrates to readers that relative polarity and absolute polarity are different. The basic statement about the diagram are explained in the prose. Repeating that you want to use your diagram repeatedly doe not make the existing one incorrect. Your constant repetition to use your diagram is verging on trolling. Please stop. 174.118.142.187 (talk) 02:34, 25 April 2013 (UTC)
 * Please note if you start the confusion technique in Polarity (mutual inductance) discussions again I will raise another ANI complaint against you. "Turns ratio" and "math equations" only demonstrate lack of understanding and have nothing to do with this article topic. Last warning. I will place this on your talk page so you cannot miss it. Thanks. 174.118.142.187 (talk) 02:39, 25 April 2013 (UTC)
 * The article should either fully explain the +/- notation as done in the link above or the +/- notation should be taken out of the diagram. To do anything different is to invite all these issues. This has nothing to do with competence. Not any more than you. I will say no more. Thanks.Cblambert (talk) 02:58, 25 April 2013 (UTC)


 * Hey guys, its really hard to follow the above discussion. Please *always* sign your names with four tildes at the end of your comment. If someone didn't sign before you spoke, please add a note about it being unsigned before you write your reply. I was asked to give my input on this discussion, but I can't do that well without a summary. Cblambert, can you please summarize what you think is wrong and how you propose to fix it? It would be particularly nice if you had a replacement image we could compare to the current one.
 * These are the points I'm hearing from you:
 * "DOT END POLARITY IS ALWAYS + POLARITY." - this is clearly not the case, as both the current diagram, and the diagrams you linked to in xformer.pdf have the dotted end on the negative polarity in some cases
 * "THE NEW DIAGRAM WITH VOLTAGE EQUATIONS IS RIGHT." - What new diagram? Can you please link to it?
 * "The article should either fully explain the +/- notation as done in the link above or the +/- notation should be taken out of the diagram." - Please, by all means, fully explain what the notation means. That would certainly help the article. However, even the source you provided (xformer.pdf) uses +/- notation and so I see no good cause to remove that notation. In fact, that notation seems critical to conveying the intended meaning.
 * "Why does article not show tests do put this issue to bed once and for all?" - wikipedia is not the place to post the results of unpublished experimentation.
 * So to be honest, I don't have the knowledge to verify that the information is correct anymore. But if you think a change is needed, please clearly post the change you want to make, and if consensus from this article's contributors is that the change should be made, then you can go ahead and make it. Because your changes are contested, consensus is needed before the change is made to the main article.
 * Fresheneesz (talk) 07:54, 26 April 2013 (UTC)

This is the Cblambert's originated drawing he had substituted into the article. Note the usage of inaccessible (locked-in) text in the image full of unrelated voltage formulae using calculus factors. Also note the usage of multiple notations for voltage, potential and emf, the unusual placement of polarity dots, and over-complexity of the drawing. This is characteristic of his editing style elsewhere (see Transformer for WP:OWNERship there in exactly the same subject matter.[]), demonstrating lack of understanding of the subject matter. The inaccessible and unrelated formulae technically frightens off most other potential editors, keeping ownership of the article. Most editors cannot or will not edit drawings and shy away. Note his usage of an unrelated turns ratio formulae "n = V1/V2 = I2/I1 = turns ratio" in the above discussion. 174.118.142.187 (talk) 13:54, 26 April 2013 (UTC)
 * In that image, why is the same voltage differential labeled as two different things (vP and eP, eS and vS, etc)? Most of my confusion about this image stem from not understanding what the 'e' variables mean. Can you explain that Cblambert? Fresheneesz (talk) 02:32, 27 April 2013 (UTC)
 * The 'e' is the electromotive force or voltage (emf) that results from the product of mutual inductance 'M' times the time derivative of current of the alternate winding's current, e.g. eS = M * diP/dt, and vice versa, eP = M * diS/dt,. Thus, if you keep iS equal to zero you can show that a positively-increasing current entering the primary's dot end produces a positive voltage at the secondary's dot end, and vice versa. Thanks.Cblambert (talk) 21:40, 1 May 2013 (UTC)
 * Three observations regarding this:
 * (1) If "iS is equal to zero" then iP, in a purely inductive winding, will be almost 90 degrees lagging eP and consequentially 90 degrees lagging eS making all that gooble-dee-gook just nonsense.
 * (2) How does the induced voltage, current or anything have to do with relative polarity markings or polarity association of windings?
 * (3) As I pointed out previously on poor terminology usage regarding polarity definitions using AC values, how can an AC current increasing from 5 amperes to 6 amperes induce a positive voltage in the secondary. I understand what you are trying to say but it isn't cutting it and you have reverted all other edits over a dozen times to this same nonsense phraseology.

174.118.142.187 (talk) 04:08, 2 May 2013 (UTC)
 * Fresheneesz asked a question, which I answereD. Your views are well known. I stand by my what I have maintained, which can be re-stated as follows:
 * THE OLD DIAGRAM IS RIGHT, BUT INCOMPLETELY EXPLAINED
 * DOT END POLARITY IS NOT ALWAYS + POLARITY BUT NEEDS TO BE EXPLAINED
 * THE NEW DIAGRAM WITH VOLTAGE EQUATIONS IS RIGHT
 * THE WORDING IN POLARITY IS RIGHT
 * LENZ'S LAW IS ALWAYS APPLIES.
 * Many thanks 187Cblambert (talk) 16:58, 2 May 2013 (UTC)

Better article title
Dot convention was a poor title and left it closed for other marking methods. Nice move Cblambert! 174.118.142.187 (talk) 23:35, 22 April 2013 (UTC)

Other marking methods - leads
I only know of two methods but I have seen many techniques for transformers with leads. I have to assume these methods are just extensions of the terminal marking methods. I have witnessed leads with H1, X1 tags, as well as white tapped or wire markers and just plain white wire insulation on one lead. I will attempt to mention these methods. 174.118.142.187 (talk) 23:35, 22 April 2013 (UTC)

Other device winding polarities
There are many other uses of winding polarity matching, namely motors use it more often than transformers. I found a lot of articles last night. Since the article has the title subject clarifier "mutual inductance" and the intentions of the markings on motor windings are for magnetic polarity matching, propulsion and attraction, (not electrical transformation) I believe (and Cblambert has previously indicated same) motor windings and other devices that need specify magnetic geography should be kept out of this article keeping wording and definition complexity out of this article. I have placed a hatnote to help eliminate future injections from drive by editors about unrelated devices. 174.118.142.187 (talk) 02:16, 25 April 2013 (UTC)


 * I suppose, but with the usual motor design there is a magnetic path between the coils, so it doesn't seem so wrong to consider it the same as transformer coupling. Gah4 (talk) 09:03, 25 June 2016 (UTC)


 * While motors and other wound components are important, let's not forget the title of this article is "Polarity (mutual inductance)" and the mutual inductance of motors where the phases are mechanically oriented at 120 degress or 90 degrees gets confusing (e.g. the mutual inductance of two 90 degree windings should be zero by theory). Certianly I agree that getting the polarity correct of motor windings is important, for example to wire a 3 phase motor as star, you need to either (a) connect all the dots together to make the neutral star point (b) connect the dot of A to the non-dot of B, dot of B to non-dot of C, and dot of C to non-dot of A to make a delta configuration, these are the only two configirations that work, anything else creates massive vibration and trips the breakers. So my point of view is that it does not belong in the body of this article , maybe a footnote or a crosslink to a motor page might be appropriate. Salbayeng (talk) 10:00, 25 June 2016 (UTC)

Right-hand rule and Polarity
Article sadly neglects treatment of right-hand rule enabling verification of the way coils are wound.Cblambert (talk) 01:00, 19 June 2014 (UTC)

Diagram is wrong
Assuming the left side of the transformer is the primary and the right side is the secondary (which should be clearly stated), the left side of the diagram is correct, but the right side is wrong. The currents and voltages should be identical on left and right diagrams. Painting a dot on a transformer doesn't magically make current flow backwards from the applied voltage. — Preceding unsigned comment added by 71.167.73.66 (talk) 13:55, 9 April 2015 (UTC)
 * It appears that power is flowing from port 1 to port 2 in the left hand pair of diagrams and from port 2 to port 1 in the right hand pair (I don't understand primary and secondary; doesn't primary refer to whichever port happens to be driven? - or is there something in the construction that means that a particular port is intended to be the driven one (seems unlikely))? In any case, the = sign between the left and right doesn't seem justified. --catslash (talk) 17:47, 9 April 2015 (UTC)


 * As far as I know, the diagram is right, but confusing. While they work both ways, we most often use transformers with voltages, and expect an appropriate value and polarity on other windings. The dots nicely tell us the voltage polarity on different windings relative to each other. Note that is true even with no current flowing in a winding! Gah4 (talk) 09:07, 25 June 2016 (UTC)


 * I'm with Gah4 on this, the dot convention relates to the instantaneous voltage being in phase , the current does what it needs to do, depending on the type of load, and transformer magnetising inductance and stray capacitance. The drawing is definately confusing (and possibly just plain wrong).

The statement "The currents and voltages should be identical on left and right diagrams" is wrong except for the non-existant case of a perfect transformer loaded with a pure resistor, with infinite magnetising inductance, zero leakage current, zero core loss, and zero capacitance. It should be borne in mind that in an inductor the current is in quadrature (at 90degrees phase shift) to the voltage, so half the time the current is in phase with the voltage and the other half the time it is antiphase, when you couple a second inductance in, and put something across the terminals, then the relationship between current and voltage will be different, but no matter what load you apply, the voltages on the wires with the dots will all be in phase.

Edit: I've just noticed the figure has changed from what it was a few months ago, the new one is simpler, but my comments about the current direction are still valid, personally I would use the current arrows in a different drawing in the transformer article, but not here. Salbayeng (talk) 10:23, 25 June 2016 (UTC)

circuit arrow
Coundn't find a detail article about "Circuit arrow", that is mentioned in this article.

Such an article exists in german wikipedia: de:Zählpfeil (I assume that's the same topic.)

--Arilou (talk) 08:25, 9 December 2015 (UTC)

More on dot and polarity
There seems to be some confusion (by people who don't really understand how transformers work) particularly regarding current flow.

Historically the dot (or knot, or tag) was used to denote the start of a winding. There is an implied assumption that all turns are wired CW or CCW only

In contemporary usage, the winding end with a dot will be in-phase in voltage to all other dot ends of windings, the current is irrelevent.

In multiwinding transformers the currents can be going in and out of all the terminals in different proportions/directions willy nilly, but the voltages will always be in phase.

The magnetising inductance can be significant and the current required to support the magnetizing inductances can be supplied from either or both windings

In cases where a transformer is supplying a leading power factor load (a large capacitor), or a transformer deliberately resonated with a capacitor , or a transformer operating above it's natural resonant frequency; then the currents will definately be reversed to those of in the figure. The statement Leads of primary and secondary windings are said be of the same polarity when instantaneous current entering the primary winding lead results in instantaneous current leaving the secondary winding lead as though the two leads were a continuous circuit is true in a physics sense only. I appreciate that it's convenient to think of a isolating transformer as a two port network where you just join the dots.

In real world practical applications, transformers are usually voltage driven, and the primary current that flows is whatever is necessary to support the magnetizing current, stray capacitance, core loss, and the load. Saying that voltage is caused by derivative of current is wrong headed thinking, like saying the horse is pushed by the cart. Current is the integral of voltage is a valid expression of Lenz's law.

The (current that flows) is the sum of (magnetising inductance x integral of the applied voltage) plus (stray capacitance x  derivative of voltage) plus (applied voltage / core loss equivalent resistance) plus (turns ratio x secondary current). The secondary current that flows is determined by how the load responds to the applied voltage.

This is just wrong, "The '+' and '-' polarities in the diagram are not the voltages driving the currents. " because the voltages are doing the driving (or being driven) they are the cause, while current is the effect.

And this is just confusing " The instantaneous directions of the current entering the primary inductor at its dotted end and the current leaving of the secondary inductor at it's dotted end are the same. " in normal english usage entering and leaving are opposites, One can see the dot analogy when driving a car in a northerly direction across a bridge, here entering and leaving are both north, but consider a fictitious department store with a revolving door on the east and west sides, futher more lets assume for every person walking in and out of the east door, four people move in and out of the west door (transformer action!), many real transformers have more than two windings. If the store were a transformer we would put a dot above the east entrance door and a dot above the west exit door, obviously because "in" and "out" are the same direction??? what about doors on the north and south side

The same muddle heading thinking is apparent in those who confuse Reaction forces and centripetal forces with real forces, the purpose of Wikipedia is to provide explanations that resolve the confusion. Salbayeng (talk) 01:55, 23 March 2016 (UTC)

Yes! Well, sometimes transformers are uses as current transformers, such as for measuring large AC currents. But as you note, most often they are used with voltages, where the dot convention easily tells us the polarity of the voltage on any winding. The polarity of the current depends on whether power is going in or out of that winding. Consider the case of a buck winding used to reduce voltage. The diagrams have two windings, but many transformers have more. Gah4 (talk) 09:16, 25 June 2016 (UTC)

spelling?
sustract each other, making the device working ineficciently 79.76.117.122 (talk) 13:38, 7 November 2016 (UTC)

Is this science or literature ??!!
Why does the author complex language to explain scientific phenomena? Please use simpler language to make them easy to understand, especially for people who are not English natives Akhilorappady (talk) 18:26, 16 January 2018 (UTC)
 * Because this is Wikipedia. Our mission is to intimidate with our smartness. --Wtshymanski (talk) 19:33, 16 January 2018 (UTC)
 * I'm not nearly as smart as the other editors, so I put down what I found in a couple of references instead of the advanced physics lecture. It's not that deep a subject...it doesn't need maths or lots of explanation. Could use a picture, I suppose.

--Wtshymanski (talk) 20:12, 16 January 2018 (UTC)

current again?
It seems that much of the article is now in terms of current again. In the case of a two winding transformer, the power into one winding has to equal (except for loss) the power out of the other. But with three or more, it isn't so simple. Dot convention works in terms of voltages, independent of which direction the current (and so power) are going on any winding. I suppose it could be done in terms of ampere-turns, also following the dot convention, and for current transformers you would likely do that. That is, the sum of the ampere-turns, following dot convention, is (about) zero. But the dot convention is more easily described in terms of voltage. Gah4 (talk) 20:12, 26 April 2018 (UTC)
 * I put this here over two years ago, and no comments. Note that using current to define the dot convention only works for transformers with two windings.  More than two, you don't know which ones power goes into, and which ones out.  That is, which are primary and which are secondary. So, the first reference I find says it is by voltage. If you want to connect windings in series or parallel, the usual case when you want phase, it is voltage related, and independent from which is primary, secondary, or neither. Gah4 (talk) 23:59, 22 May 2020 (UTC)
 * OK, if you need a current rule, the sum of the ampere-turns into dot windings is zero. Considering each part of a multi-tap winding separately. Since transformers with multiple windings, or extra taps with only two, are common, this distinction is needed. Gah4 (talk) 00:07, 23 May 2020 (UTC)
 * Here is another that explains dot convention for voltage. I don't believe that the current definition is the definition, but it is a definition. But the voltage definition is most useful for connecting primary or secondary windings in series or parallel, which is the most common use for dot convention. The current definition does not make it easy to know how to wire up series or parallel windings.  Gah4 (talk) 01:41, 24 May 2020 (UTC)
 * OK, if you need a current rule, the sum of the ampere-turns into dot windings is zero. Considering each part of a multi-tap winding separately. Since transformers with multiple windings, or extra taps with only two, are common, this distinction is needed. Gah4 (talk) 00:07, 23 May 2020 (UTC)
 * Here is another that explains dot convention for voltage. I don't believe that the current definition is the definition, but it is a definition. But the voltage definition is most useful for connecting primary or secondary windings in series or parallel, which is the most common use for dot convention. The current definition does not make it easy to know how to wire up series or parallel windings.  Gah4 (talk) 01:41, 24 May 2020 (UTC)
 * Here is another that explains dot convention for voltage. I don't believe that the current definition is the definition, but it is a definition. But the voltage definition is most useful for connecting primary or secondary windings in series or parallel, which is the most common use for dot convention. The current definition does not make it easy to know how to wire up series or parallel windings.  Gah4 (talk) 01:41, 24 May 2020 (UTC)