Talk:Transformer/Archive 16

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The role of the magnetic vector potential in transformers

First, an analogy. I can compute the velocity of my car by computing the time derivative of the number displayed on the odometer. That doesn’t mean the odometer causes the car’s velocity. The relationship holds because they are both caused by the same thing, which is the motor. Faraday's law of induction (FLI) states that the EMF (path integral of the electric field) in closed loop is proportional to the time derivative of the total flux the enclosed in the loop, including the flux in the core. This is a very useful relationship for designing transformers and predicting their behavior. This doesn’t mean that the flux in the core causes the EMF in the secondary, although it is often taught that way. Most of the time, that is good enough. But, in fact, if the flux in the core actually caused the EMF in the secondary, that would be action at a distance. Feynman makes this point in Volume 2 of the Feynman lectures, chap 15 section 5 in the second paragraph following equation 15.36.

Modern physicists have worked very hard to eliminate action at a distance. The modern formulation is that the currents produce the magnetic vector potential, A, at the wires. A produces a component of the electric field, E in accordance with E = -∂A/∂t (actually E= -∇φ -∂A/∂t, but I am ignoring φ). The line integral of -∂A/∂t over a closed path is the EMF. Faraday’s law of induction (FLI) works because B = ∇ × A; E at the wires has the same cause as B in core. FLI is useful for engineers because they almost always have the transformer connected to a circuit which provides a complete path. However, E = -∂A/∂t, gives the E field at each infinitesimal part of the path.

I am not going to try to put this in the article; it is probably too technical. I’m not going for WP:RGW, but I will try to edit the article so it is not in conflict with the modern formulation. For example, instead of “EMF is caused by the changing flux in the core” I may write “EMF is equal the rate of change of the flux in the core.” The first version is simpler and more direct, but it is a fiction whereas the second version is a correct statement.

BS? Your comments are invited.Constant314 (talk) 02:41, 9 December 2018 (UTC)

This is going over my head but I wish we could find a more accessible alternative than the proposed “EMF is equal the rate of change of the flux in the core.” Is there a word besides "caused" that could be substituted in the simpler version? ~Kvng (talk) 15:34, 2 March 2019 (UTC)

Real transformer

I think there is an error in the diagram of a real transformer. The indicated current Is should, in my opinion, be Is/a, the transformed value of the secondary current. Madyno (talk) 21:49, 18 March 2019 (UTC)

The designations are for the current in the wire. In general, it is not the case that I_s = a x I_p because I_p includes magnetizing currents. Constant314 (talk) 22:02, 18 March 2019 (UTC)

I don't say $I_{s}=a\cdot I_{p}$. It is quite common to call the secondary current $I_{s}$. I think the system used in the diagram is to use an accent for the transformed quantities, note $X',R'$. Which means the current should read $I'_{s}=I_{s}/a$. Madyno (talk) 17:21, 19 March 2019 (UTC)

Sorry, I think that I was confused about which figure. Are you talking about the figure labeled "Real transformer equivalent circuit"? Constant314 (talk) 17:40, 19 March 2019 (UTC)

Indeed, and sorry, I was confused about the meaning of the transformation ratio a. I've corrected it. Madyno (talk) 21:20, 19 March 2019 (UTC)

I get that wrong about half the time. Constant314 (talk) 22:50, 19 March 2019 (UTC)

Yet the diagram "Real transformer equivalent circuit" shows an error, or at least a confusing use of the symbol $I_{s}$, which should be, in my opinion: $I'_{s}=I_{s}/a$. The symbol $I_{s}$ is quite commonly used for the secondary current. Madyno (talk) 09:48, 20 March 2019 (UTC)

I agree, that is the way I would draw it. But, we have the diagram that we have, which supposedly came from a reliable source. You can replace the diagram if you have a reliable source, or if you have the the original source (appears to be Daniels) and find that the diagram was different in the original source. But it needs to have the same level of detail. Or you could redraw it and put in I_s/a in place of I_s and propose it here on the talk page as an improvement, but you might get resistance. Sorry, there is no simple way to edit a figure. By the way, please use leading colons to indent your comments. Constant314 (talk) 18:18, 20 March 2019 (UTC)

We could just comment on this in the text underneath the diagram. Madyno (talk) 21:06, 20 March 2019 (UTC)

That would be even more confusing.Constant314 (talk) 23:27, 20 March 2019 (UTC)

I corrected the drawing, but was not able to download it to Commons.Madyno (talk) 22:50, 20 March 2019 (UTC)

The description of the figure is controlled by the description given in the file invocation in the article. But what were you going to change the description to? Constant314 (talk) 23:34, 20 March 2019 (UTC)

TREQCCT.jpg diagram is ok as shown, I' denoting referred to the primary. Hence, I' = Is/a. See Ideal transformer equations box which says that "the superscript ' denoting referred to the primary.Cblambert (talk) 23:41, 20 March 2019 (UTC)

[Sorry for not following the indentation here] I gave the following comment on the talk page of Cblambert.
The primary current is $I_{p}$, the secondary current is commonly denoted as $I_{s}$, just as in the box with Ideal transformer equations. The backwards transformed quantities are denoted with a prime, like $X'_{s}=a^{2}X_{s}$ and $R'_{s}=a^{2}R_{s}$. For some reason the secondary current itself is not indicated in the diagram. Yet it would be more consistent and less confusing to denote the backwards transformed secondary current with $I'_{s}=I_{s}/a$. The remark that the prime refers to the primary circuit, means the primed quantities are to be considered as part of the primary circuit (in the equivalent circuit), and hence exactly that the indicated current $I_{s}$ should be written as $I'_{s}$. Madyno (talk) 09:59, 21 March 2019 (UTC)

Here is the latest circuit:

I find it agreeable. Are there instances in the text where Is' should be changed to Is os Is to Is'? Perhaps it should also show Es=Ep/a or Ep=a Es. Constant314 (talk) 14:31, 21 March 2019 (UTC)

TREQCCT.jpg diagram is ok as shown. There is a big difference between 'prime refers to the primary circuit' and 'the superscript ' denoting referred to the primary'.Cblambert (talk) 14:50, 21 March 2019 (UTC)

Yes, I agree that 'prime refers to the primary circuit' is inaccurate since there are clearly variables in the primary that do not have the primed superscript. 15:00, 21 March 2019 (UTC)

I do not say the picture is wrong, but it is definitely confusing. The current in the circuit, denoted by $I_{s}$ is NOT the secondary current as it suggests to be. It would be more consistent to call it $I'_{s}$ and write $I'_{s}=I_{s}/a$, and put $I_{s}$ as the secondary current in the secondary circuit. Note that in the box Ideal transformer equations the secondary current is also called $I_{s}$. The primed symbols all refer to quantities from the secondary circuit, that may be considered to be part of the primary circuit if they are transformed backwards. Well, this is all a repetition of what I wrote above. Why is this so hard to understand? Madyno (talk) 19:02, 25 March 2019 (UTC)

I don't understand your comment. I_s is the current coming out of the secondary terminal. I_s is the actual secondary current of an actual transformer. That is what the drawing above shows. Constant314 (talk) 19:28, 25 March 2019 (UTC)

I hardly can believe you really write this! The secondary terminal is completely at the right of the picture. No sign whatsoever of a symbol - let alone the symbol $I_{s}$ - to indicate the secondary current. Have a better look at the drawing right above. ?????Madyno (talk) 21:29, 25 March 2019 (UTC)

A miracle has happened! The original drawing we're talking about is the one above. In the mean time the corrected picture I made, is now shown in the article. So, all's well, that ends well. Madyno (talk) 21:49, 25 March 2019 (UTC)

I better say, a lot of unexpected events happen. In the article the corrected version is shown. On the talk page - on my computer at least - the old picture appears. However, when I click on the picture, the new version shows. When I have a look at Commons, it shows I seemed to have succeeded in uploading the new version. But the picture shown next to my user name is the old version. But then again, when I click on it, the new version comes up. It's magic, but not of the kind I like on Wikipedia. Madyno (talk) 22:02, 25 March 2019 (UTC)

Yes that happens to me. I think my browser thinks that it already downloaded the image. Glad we all see the same picture now.Constant314 (talk) 00:19, 26 March 2019 (UTC)

Indeed, must have been the cache of the browser. Sorry for the inconvenience. At least the picture now is correct, as far as I can see. Madyno (talk) 08:39, 26 March 2019 (UTC)

Necessity of bibliography

The preferred practice now is that on the first use of a reference in the article, you give the reference a name and then include the full bibliographic information. After that, you just use the name. For example, reference #3 uses this style. Here it is: <ref name="Bedell (1942)">{{cite journal|last1=Bedell|first1=Frederick|title=History of A-C Wave Form, Its Determination and Standardization|journal=Transactions of the American Institute of Electrical Engineers|volume=61|issue=12|page=864|doi=10.1109/T-AIEE.1942.5058456|year=1942}}</ref>

However, when this article was written, it was using the convention that the full bibliographic appears in the bibliography and each inline reference just gives enough information to find the entry in the bibliography.

For example, the fourth reference (it is in the Ideal transformer equations yellow box on the left of the Ideal transformer section) is <ref>{{harvnb|Skilling|1962|p=39}}</ref>

If there is no bibliography and if you click on the fourth reference, you get “Skilling 1962, p. 39”. That’s all you get. That is not the full bibliographic entry.

If there is a bibliography is present, you get “Skilling, Hugh Hildreth (1962). Electromechanics. John Wiley & Sons, Inc.” Without the bibliography, the reference is incomplete.

However, if there are entries in the bibliography that are not used in the article those can be removed. Constant314 (talk) 14:09, 16 April 2019 (UTC)

Why not convert the previous format to the new one? --Ita140188 (talk) 14:56, 16 April 2019 (UTC)

That would be ideal, but there are a lot of entries and opportunity for error. But until converted, we still need the bibliography, although it can shrink as it is converted. Constant314 (talk) 16:38, 16 April 2019 (UTC)

What a mess. Why does "harvb" even exist? I've put it back, I'm an old man and I won't live long enough to fix this. --Wtshymanski (talk) 17:46, 16 April 2019 (UTC)

I think it is called Harvard style. Blame them. It was used a lot ten years ago. Reference style keeps evolving on WP. I support your efforts to trim references. Constant314 (talk) 21:28, 16 April 2019 (UTC)

We just need to show that we're not making it up, we don't need to survey 22 different conference proceedings for things like "Some transformers are painted green" --Wtshymanski (talk) 21:47, 16 April 2019 (UTC)

Thanks for the cleanup work! To keep the page number and to avoid duplicating a lot of references you can also use Template:rp. --Ita140188 (talk) 09:38, 17 April 2019 (UTC)

Thank you for the pointer to Template:rp, although the documentation for it is quite luke-warm on recommending it as a reference style. Since this article already has mixed systems, it won't make things any worse if any are converted out of the "harvnb" style. --Wtshymanski (talk) 00:37, 19 April 2019 (UTC)

Principal's word view problem

The principal's for transformer induction are some hided on one sided and can't viewed Jake Holt (talk) 08:56, 13 July 2019 (UTC)

It looks fine on my laptop using the Chrome browser. Sometimes there are problems viewing on a small screen devices. 16:10, 13 July 2019 (UTC)