Talk:Transformer/Archive 8

Copper losses etc.
@Cblambert, do you really think that "lower advantageous resistive conductor circuit losses" is more intelligible than "less power is lost by dissipation in conductor resistance"? I also think it was mistaken to remove "the voltage must be reduced to the voltage required at the user's equipment." The two majopr purposes of transformers (in AC power distribution) are step-up for distribution and step-down to something safe for the user. One is the corollary of the other and should rightly be mentioned here.  Spinning Spark  08:09, 7 October 2012 (UTC)
 * Did not see this until now. I assume this is not an issue anymore . . .Cblambert (talk) 18:44, 4 January 2013 (UTC)

PRI and SEC
Does anyone, beside the editor trying to edit war this in, think that these abbreviations add anything to the article?  Spinning Spark  23:22, 3 November 2012 (UTC)
 * no Constant314 (talk) 23:36, 3 November 2012 (UTC)

power converter or just electrical device?
The lede contained the description "A transformer is a power converter that transfers energy..." I reverted the change of User:Wtshymanski, who changed it into "A transformer is an electrical device that transfers energy...", with a cryptic edit summary. I like to understand what is wrong with the more specific classification power converter? I'm not aware of transformers not falling under this classification. Thanks, SchreyP (messages) 23:02, 29 December 2012 (UTC)
 * It is a power converter of course, but that is not the essence of what it does and the wikilink is not particularly useful to the reader. If we are going to say that at all, the first sentence of the lede is not the right place.  Spinning  Spark  23:35, 29 December 2012 (UTC)
 * Ok, explanation accepted. Also the edit summary during the second revert by User:Wtshymanski was this time more clear ("revert; give specific type of apparatus instead of hokey redirect...") Thanks, SchreyP (messages) 12:16, 30 December 2012 (UTC)
 * Also a "power converter" is only one role a transformer can be used for. They also can be (and frequently are) used to match and isolate and block DC in signal transmission. Plugwash (talk) 11:46, 31 December 2012 (UTC)
 * I saw someone preface another article a '. . . a passive electrical device . . .'; maybe this would fit.Cblambert (talk) 07:07, 4 January 2013 (UTC)
 * I think the first paragraph could be reworded so that inductive coupling only appears once.Constant314 (talk) 03:23, 16 January 2013 (UTC)
 * I agree about eliminating inductive coupling. I saw it again this article and it was '. . . a static device . . .'. Lineman's handbook citation also refers to '. . . a static device . . .', which is why I changed it to '. . . a static electrical device . . .'. It is hard to judge when to act, when to talk . . .CblambertCblambert (talk) 20:05, 16 January 2013 (UTC)

Equivalent circuit
Having recent had a stab as creating new Steinmetz equivalent circuit section, I have a few problems with Equivalent circuit section. And so on and so forth. I welcome any and all comments.Cblambert (talk) 08:03, 4 January 2013 (UTC)
 * Section adds little to the section but laboriously regurgitates already cover content.
 * Wording puts the cart before the horse in referring $$R_S$$ and $$X_S$$ to the primary. Diagram should accordingly be replaced by [[File:TREQCCT.jpg]]
 * Transformer equivalent circuit should be linked to rich available historical background.
 * Sauce good for the goose Equivalent circuit should be sauce good for the gander Steinmetz equivalent circuit. That is, the two section should be, harmonized because the two are so closely related.
 * Any eventual referring of $$R_S$$ and $$X_S$$ to the primary should NOT include the ideal transformer. The whole point of equivalent circuits is to simplify things as much as possible. This is what is done in practice:
 * Do a transformation looking at everything from the primary side.
 * Do another transformation looking at everything fromt the secondary side.
 * And so on.
 * All self-respecting AC power analysis should preface reactances with the j letter 90 degree rotation operator with good reason.
 * Equivalent circuit should inject so realism, rules of thumb, anything to connect the article to transformer practice. For example, like to basic Transformer parameters like impedance and voltage regulation.
 * Link at http://www.electrical4u.com/electrical-transformer/equivalent-circuit-of-transformer.php provides good treatment of earlier comment above, including in terms of needing to look at transformations referred to both primary side and secondary side, which in turn is as done in Steinmetz equivalent circuit.
 * Note also that Equivalent circuit needs to clarify that circuit is single-phase presentation valid in steady-state only.
 * In Equivalent circuit, what is meant by '. . . Saturation effects cause the relationship between the two to be non-linear, but for simplicity this effect tends to be ignored in most circuit equivalents. . . .'?Cblambert (talk) 21:07, 5 January 2013 (UTC)
 * I think it is simpler and easier to understand if the secondary impedances are on the secondary side of the ideal transformer.Constant314 (talk) 11:51, 12 January 2013 (UTC)
 * Noted.Cblambert (talk) 20:12, 14 January 2013 (UTC)
 * I also think that the inductances should be Lp and Ls, not jXp and jXs. I understand exactly what you mean, but it is too technical.  Anyone who understands what you mean does not need to see the explicit use of the j operator and anyone who doesn't will just be confused.Constant314 (talk) 11:56, 12 January 2013 (UTC)
 * With all due deference to Proteus, I have sort of come around to the same thinking. As short term fix, I could come up with change to TREQCCT.jpg easily enough but will ponder this for a while more pending more comments. However, transformers and other electrical machines and j concept are collectively probably too important to be ignored in longer term in treatment of related Wikipedia articles. Also, such articles should make clear that sll types of equivalent circuits 'are physically identical and lead to same results' and 'a suitable choice of the transformation is a question of expedience'.Cblambert (talk) 20:12, 14 January 2013 (UTC)
 * Delay in showing conversion without j, because of huge problem purging Wiki Commons image. Amazingly, only way to purge cached images of late is by increasing image size to 840px!! It is unclear is this is due to my computer or is a generalized problem. If the the latter, this would be incredible Wiki Commons problem. But anyway here is equivalent proposed new equivalent circuit sans the j.Cblambert (talk) 21:41, 20 January 2013 (UTC) TREQCCT.jpg

Components or parameters
I think that converting all instances of component to parameter may be a mistake. I prefer that we use the best word in each instance, even if that means we have both components and parameters. Circuits, even equivalent circuits, are composed of components. Even if those components represent parameters of the transformer. Thus, when we talk about R_sub_P we should use the word component. When we talk about its value we can use the word parameter. We can also say that the component represents a parameter of the transformer or that value of a component is the same as a parameter of the transformer.Constant314 (talk) 18:24, 5 January 2013 (UTC)
 * I am easy. Component infers something that is a physical, real, which is not the case in a transformer equivalent circuit. Hence, parameter is probably more appropriate . . .?Cblambert (talk) 19:46, 5 January 2013 (UTC)
 * I think the elements of equivalent circuits are components even it they are not physical.Constant314 (talk)
 * IEEE 112, IEEE Standard Test Procedure for Polyphase Induction Motors and Generators, which makes extensive use of euivalent circuit, makes no mention of 'component' in relation to equivalent circuit but does refer to 'machine parameters of the equivalent circuit' and 'motor parameters have been determined from the no-load and locked-rotor tests'. Only mention of 'component' is in relation to 'component of stray load loss is not available', 'each of the components of the loss', 'various components with stray-load loss', and 'pulsating component of current'. 'Parameter' does seem more appropriate.Cblambert (talk) 01:28, 6 January 2013 (UTC)


 * "Component" is a particularly bad term to use in our field where it invariably refers to a physical item. In network theory we talk about elements which immediately indicates we are talking about idealized abstracted items.  Although the elements of an equivalent circuit can often be identified with a physical component, in many cases this is not so and the elements bear no relation to the physical circuit at all.  As an example, consider a delta connected three-phase transformer.  It is quite straightforward to find an equivalent circuit star connected transformer.  However, the windings of this new equivalent circuit cannot be mapped on to the physical windings at all.  Spinning  Spark  17:41, 6 January 2013 (UTC)
 * I suppose the components of a transformer are the iron, the wire, the insulation etc. I would prefer elements over parameters then when discussing the equivalent circuits.Constant314 (talk) 02:13, 7 January 2013 (UTC)
 * In connection with AC machine equivalent circuit parlance, the much more usual expression is parameters, which can be verified by a cursory look in IEEE Xplore abstrasts. Also browse through websites such as http://www.electrical4u.com/electrical-transformer/equivalent-circuit-of-transformer.php and http://www.ece.ualberta.ca/~knight/electrical_machines/induction/basics/circuit.html. AC machine equivalent circuit parameters are typically derived from tests whereas implication is from Spinningspark's comment above that element is used for more or less precise circuit abstraction definition purposes. The term component invariably denotes either a smaller, lighter current device or as IEEE 112 suggests some sort of contribution, part to things like 'stray loss', 'current', etc.. Cblambert (talk) 18:49, 7 January 2013 (UTC)
 * Another AC machine equivalent circuit usage is treatment by P.L. Alger et al. in 'Induction Machines' section of old Knowlton EE handbook which refers simply to either equivalent circuit 'contants' or 'impedances' throughout, 'impedances' being used as caption in separate impedance circuit diagram along with a long listing of 'Definitions of Equivalent-circuit Constants'. No elements, no parameters, no components. Use of term 'parameter' may have evolve somewhat since. Moral in all this is perhaps that equivalent circuit parameters should be used but as sparingly as possible.Cblambert (talk) 19:42, 7 January 2013 (UTC)
 * It seems to me that the items that make up the equivalent circuit are entities that may have parameters but are not parameters. Of course the parameter of an element might be the same as a parameter of the transformer.  So I suppose it comes down to careful language.  Are you referring to a parameter of the transformer or an element of the equivalent circuit?  Anyway, my concerns have been heard.  I'm satisfied.Constant314 (talk) 00:22, 8 January 2013 (UTC)

Series-looped parameters or just series
I think the construct  series-looped sounds like specialty jargon and is confusing. In most cases, if not all, the word series by itself is adequate and more commonly used.Constant314 (talk) 18:30, 5 January 2013 (UTC)
 * Here again, I'm easy. Would series loop seem less jarring? We are talking about equivalent circuit so some distinction is needed between shunt leg and the outer loop all around . . .Cblambert (talk) 19:52, 5 January 2013 (UTC)
 * Eventually changed to 'series loop' in 1st instance, 'series' in 2nd instance.Cblambert (talk) 20:24, 5 January 2013 (UTC)

Types?
I was going to start a section on RF transformers but... Should we be expanding this section or collapsing it to include just brief descriptions of transformer types with a link Transformer types for more detail? If we do not the whole thing and details would be a duplicate of the other article. This article has the potential (pun intended) to become huge and very clumbsy. There is a lot of ground to cover, yet, as we break away from just power transformers. This may be a good way to keep some of the article size down. 174.118.142.187 (talk) 03:13, 11 January 2013 (UTC)
 * I'd like to see the stuff specific to large industrial and power company transformers moved to its own page.Constant314 (talk) 11:43, 12 January 2013 (UTC)
 * I agree. There are way too many signal, RF and weird transformers to lump them all into one article. Perhaps an intro/disambiguation page with transformer basics branching into various articles on power (industrial) transformers (>1 kVA), power supply transformers (<1 kVA), signal, rf, etc.. (or perhaps just small transformers?). Sections and statment could be moved from one to the other if they pertain to another sub-article. There are already a bunch of articles out there that repeat a lot of info. 174.118.142.187 (talk) 16:52, 12 January 2013 (UTC)
 * There's parts catalogs out there for details. This article should give general principles and just point at the rest of the types that are made. --Wtshymanski (talk) 18:52, 13 January 2013 (UTC)


 * For what? All these power electronics articles are full of anecdotes written by wire connection technicians. Fact checking and source finding is a higher priority right now. Cantaloupe2 (talk) 19:01, 13 January 2013 (UTC)
 * I too strong suport idea that portions specific to large industrial and power company transformers should be moved to own article, possibly using Distribution transformer renamed Power and distribution transformers for the purpose.Cblambert (talk) 22:48, 13 January 2013 (UTC)
 * I removed the duplicate info, transferring some were I didn't find duplicate info, in order to compact this article. Much more needs to be done in order to prepare to clean this article out as Wtshymanski suggested and I agree with him. This article has become a repetitive tidbit junk drawer. 174.118.142.187 (talk) 00:15, 14 January 2013 (UTC)
 * Sudden yanking of Types section content raises questions as to whether some content better than that replacing Transformer types disappeared. Some attempt should be made to merge best content from each article in Transformer types.Cblambert (talk) 01:19, 16 January 2013 (UTC)
 * I love what you (and SS) have done with the section. More pro looking. 174.118.142.187 (talk) 07:24, 16 January 2013 (UTC)


 * The dividing line of 1kVA some anonymous editor suggested is completely arbitrary and I oppose using that as point of reference. Cantaloupe2 (talk) 23:45, 13 January 2013 (UTC)
 * Definitely arbitrary. I have heard it used before but there is no clear dividing line based on electrical rating. The formula may be complex not well defined and there may be some crossover, for sure. The formula will most likely not be mentioned in any article. OTOH it may be the disambiguation line in the article to redirect readers and editors to stay in the correct teritory. I doubt we will find a perfect one. There will always be exceptions. It will definitely require technical people and lots of input to find major exceptions and write them in using 20 words or less :) 174.118.142.187 (talk) 00:06, 14 January 2013 (UTC)

'Notes' and 'References' sections misnomers?
Following suggestion by Spinningspark, I've reverted back to original 'Notes' and 'References' section headings in order to table here for consideration. I accordingly suggest and invite comments about the following section heading title changes:
 * Existing 'Notes' section headingh to be changed to new 'References' heading
 * Existing 'References' section heading to be changed to new 'Bibliography' heading.

Any new 'Notes' section heading could then be used for explicit notes with text.Cblambert (talk) 21:14, 13 January 2013 (UTC)


 * I don't know why this article is different than almost every other article. The section references contains a reflist. What more do wee need to label it that way? 174.118.142.187 (talk) 00:09, 14 January 2013 (UTC)
 * Refer to the following excerpted paragraph from recent VFD GA review Talk:
 * "There is this Citing sources, and if you wish to see a good example of a GA using that style try Leoš Janáček. Arguable this is Scientific article (well, engineering) so there is also Scientific citation guidelines. Pyrotec (talk) 20:09, 20 May 2012 (UTC)"


 * The source citing scheme for Leoš Janáček article is as follows:
 * == References ==
 * ===Notes===
 * Reflist|2
 * ===Sources===
 * refbegin|2
 * ===Further reading===


 * So I think Transformer had good intentions which got confused with 'References' instead of 'Sources' and which did not follow through with proper 'Notes' along lines above.


 * I agreed with the VFD GA reviewer to the following simple citing scheme:
 * ==Notes==
 * notelist
 * == References ==
 * reflist


 * Which is along the lines of the way it is now done for Transformer, whereby 1st instance of source is spelled out in full per templates, following instances of sources being shown in current abbrteviated format, on the basis that this what I am accustomed for engineering practice.Cblambert (talk) 06:20, 14 January 2013 (UTC)Cblambert (talk) 17:49, 14 January 2013 (UTC)


 * I think Cblambert's change is a great improvement and should be kept. By the way, I had not meant to suggest that the change should be reverted.  Spinning Spark  20:24, 14 January 2013 (UTC)

Zig-zag?
I understand that "zig-zag" is a winding configuration and not a major transformer type as discussed in this article. "Zig-zag is a nickname used by EE people as a shortform description. Should the term "grounding transformer" be used more appropriately? We don't refer to transformers as "delta" or "wye" for their types. Many power transformers have zig-zag wndings but are not referred to as zig-zag, delta or wye to describe them as their major descriptor. It only describes one winding. Also, there are other winding configurations used for grounding trasformers. Anybody have sources for the official usage of this name? 174.118.142.187 (talk) 17:12, 17 January 2013 (UTC)
 * I could not disagree with you more. Transformer article is part of Electrical engineering WikiProject. Zig-zag term is a very well known term, on a par with delta, wye, and autotransformer, which is used for both phase-shifting and grounding purpose. Is Wikipedia an encyclopedia or not? Where does Wikipedia draw the line on truth?Cblambert (talk) 22:24, 17 January 2013 (UTC)
 * Re official usage, have a look as Lawless reference, which provides all the various EIC winding configuration combination.Cblambert (talk) 22:29, 17 January 2013 (UTC)
 * Strawman arguments. "Zig-zag" being a term or its importance is not disputed. Please read what I wrote. Would you describe all the transformer types under the zig-zag heading all over again? e.g. "Zigzag/wye tr.", "zig-zag/delta tr.", "zig-zag/zig/zag tr.", "zig-zag grounding tr." I believe people, here using "zig-zag transformer" are referring to a "zig-zag grounding transformer". Should we mention the "star/delta grounding transformer" also? We haven't been  entering transformer types as "star transformer", "delta transformer" or "open delta transformer". Types have been listed by their distinct functions. 174.118.142.187 (talk) 22:48, 17 January 2013 (UTC)
 * The current issue is the importance of zigzag in no far as showing zigzag Types category in Transformer. According to Lawless and EIC delta is delta, wye is wye, autotransformer is autotransformer and zigzag is zigzag. Further, details should go in Zigzag transformer article. IEEE Xplore gives about 50 titles of zigzag transformer search, another 50 titles for zig-zag transformer search.Cblambert (talk) 23:05, 17 January 2013 (UTC)
 * See also, which defines 4 general winding configuration letter designations: D or d for delta, Y or y for wye or star, Z or z for interconnected star or zigzag, and N or n for neutral brought out to terminal (ie, not a winding phase), where uppercase is primary and lowercase is secondary. Note change making distinction for General winding configuration type according to IEC vector group or 'other'.Cblambert (talk) 02:05, 18 January 2013 (UTC)
 * You have only provided strawman arguments, refusal to understand and discuss the actual issue, article links to articles that do not exist, references that are behind paywalls, obscure Lawless reference, and a Google book that both agree with my initial post and (the book never once mentions "zigzag transformer"). I have to reject your input to this discussion. Now I see you have gone and editted more of the same confused thinking into the Transformer type section while we are discussing it? We need to wait for other fresh input and eyes. 174.118.142.187 (talk) 02:22, 18 January 2013 (UTC)
 * We will see. All this seems to be too much for some to absorb. Please provide specific arquements to points. No sweeping generalizations. Please.Cblambert (talk) 03:09, 18 January 2013 (UTC)


 * And what is your contention with paywall? Verifiability do not require openly accessible for free through WWW. Cantaloupe2 (talk) 09:42, 18 January 2013 (UTC)
 * See WP:PAYWALL. There is nothing in our rules about free. Cantaloupe2 (talk) 12:02, 21 January 2013 (UTC)

Here is way another source puts it: "Winding connection designations

First Symbol: for High Voltage: Always capital letters. Second Symbol: for Low voltage: Always Small letters. Third Symbol: Phase displacement expressed as the clock hour number (1,6,11)
 * D=Delta, S=Star, Z=Interconnected star, N=Neutral
 * d=Delta, s=Star, z=Interconnected star, n=Neutral.

See link at http://electrical-engineering-portal.com/understanding-vector-group-transformer-1 Where interconnected star & zigzag used interchangeably. All of this as been known for over half a century.Cblambert (talk) 03:38, 18 January 2013 (UTC)


 * Still another source, p. 105. Zigzag pretty clear. Very good source, by Shoaib Khan.Cblambert (talk) 04:03, 18 January 2013 (UTC)
 * I rest my case with this source: http://www.transformerworld.co.uk/vector.htm.Cblambert (talk) 04:31, 18 January 2013 (UTC)

In South Africa, it is called zig-zag here

This is a German book in English. Page 89-92 is a wealth of information on zig-zag. And it calls it that. here Cantaloupe2 (talk) 09:38, 18 January 2013 (UTC)
 * I looked over Cblambert's references. It seems that that zigzag is used to describe a type of winding (such as Wie or Delta) and it is also used to describe a type of transformer.  It seems the most common usage is in grounding, but it has other uses.  I think that the only thing that needs to be done is to explicitly write either zigzag winding or zigzag transformer.Constant314 (talk) 13:54, 18 January 2013 (UTC)
 * Beeman reference says on p. 349: 'Grounding transformers may be either of the zigzag or Y-delta type.' and provide excellent treatment of both types.Cblambert (talk) 00:24, 19 January 2013 (UTC)

On more careful reading, that should have/now read, I gather from the three previous comments about paywall, free, www and so on that this is no longer an issue.'Cblambert (talk) 18:24, 22 January 2013 (UTC)

Error in Transformer universal EMF equation?
In Transformer universal EMF equation and in
 * $$ E_\text{rms} = {\frac {2 \pi f N a B_\text{peak}} {\sqrt{2}}} \! \approx 4.44 f N a B$$

$$B_\text{peak}$$ becomes $$B$$.

What's wrong (2*pi/sqrt(2)≈4.44...)?

212.152.15.118 (talk) 16:44, 23 January 2013 (UTC)
 * I agree. There are several issues:
 * Re 1st equation line
 * $$a$$ is not defined; it should be defined in SI system as square meter unit
 * $$B_\text{peak}$$ should be used instead of using $$B_\text{peak}$$ and $$B$$
 * as 4.44 is accurate to 2 decimal places $$=$$ should be used instead of $$\approx$$
 * N is not defined as to which winding relates to which emf
 * ie, emf of respective winding should read
 * $$ E_\text{rms} = {\frac {2 \pi f N a B_\text{peak}} {\sqrt{2}}} \! = 4.44 f N a B_\text{peak}$$
 * Re 2nd equation line
 * This is also an issue here as Knowlton reference (p. 38, equation 2-36, Sec.2-32) suggests that 2nd equation line should, for any half cycle interval of time $$t_2 - t_1$$, read:
 * $$ E_\text{avg}= 2 N a B_\text{peak}/(t_2-t_1)\!$$ and not $$ E_\text{avg}= 4 f N a B_\text{peak} \!$$.
 * Cblambert (talk) 20:52, 23 January 2013 (UTC)

Lede
What is "... or winding circuits" adding to the definition?  Spinning Spark  18:46, 16 January 2013 (UTC)
 * Autotransformer says one winding. See also Types which refers to circuits.Cblambert (talk) 19:16, 16 January 2013 (UTC)
 * Maybe '. . . two or more of its windings or circuits of the same winding.' would be better.Cblambert (talk) 20:10, 16 January 2013 (UTC)
 * It's a little confusing. Definitely fringe. Can't an autotransformer have a primary winding and a secondary winding even though some winding turns are shared? They are still linked inductively, and act as the rest of the breeds, otherwise current transformation could not occur. 174.118.142.187 (talk) 21:24, 16 January 2013 (UTC)
 * I tend to agree but one winding is definitely not two or more windings. I am comfortable with '. . . its winding circuits. Grounding zigzag transformers also don't have 'two or more windings', which is why you can ground them. Polygon transformers, used on input to VFDs, don't have 'two or more windings'. . .Cblambert (talk) 00:26, 17 January 2013 (UTC)
 * That phrase is a good compromise, for lack of a beter one that covers the continguencies. Zig-zag windings on grounding banks were never called transformers in my world. They have no secondary and do not transform voltages (in the usually defined way) Zig-zag windings on transformers are just another shape of wye winding configuration. I am not very familiar with VFD technology. 174.118.142.187 (talk) 02:54, 17 January 2013 (UTC)
 * Zigzag transformer exists in wikipedia world and real world. And yes zigzag bank is often used but the two terms, transformer and bank, are not mutually exclusive. Phase-shifting zigzag transformers have two windings, which are definitely transformers. And, zigzag are often evidently derived from two-winding transformers judging from Lawless citation, but I have see them customized for fit-for-purpose grounding application. The point is that caution is in order in lede woring regardless of grounding zigzag definitive description. Polygon transformer details are not very common on the web but windings are exactly that, polygon in physical configuration.Cblambert (talk) 03:24, 17 January 2013 (UTC)
 * Knowlton, p. 550 says 'A grounding transformer is a transformer primarily for the purpose of providing a neutral point for grounding purposes.' Ergo, hence, grounding transformer seems ligit. And zigzag transformer being a special type of grounding transformer also seems ligit.Cblambert (talk) 03:34, 17 January 2013 (UTC)
 * Yeah, a zig-zag grounding transformer falls about the same spot as an autotransformer. Not all grounding transformers are zig-zag windings and not all zig-zag transformer windings have anything to do with grounding. I have worked with both types of grouding banks. I built one out of three 5 MVA trans. once for a 40MVA delta transformer system conversion. :) (I guess "bank" is a just short form of "transformer bank"). You would be an interesting guy to reminisce with. 174.118.142.187 (talk) 04:43, 17 January 2013 (UTC)
 * Lawless citation uses zigzag term throughout but I'm used to and more comfortable with zig-zag. Also, Lawless talks of zigzag grounding banks . . . Cblambert (talk) 05:11, 17 January 2013 (UTC)

Here is, compliments of Block, VDE/IEV-based approach to LEDE:
 * 'A transformer is a static device with two or more coils which transforms a system of alternating voltage and alternating current through electromagnetic induction, usually with different values but the same frequency, for the purpose of transmitting electrical energy.'
 * Cblambert (talk) 19:09, 28 January 2013 (UTC)