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I added a section outlining the balanced wye conneced and delta connected modes. The circuit diagrams with generator side offer more to the reader than the other two delta and wye diagrams. The voltage and current derivations add more to the story of where the VLL and VLN conversions come from than in the single phase load section. I would consider also consolidating the single phase load section moving its Unbalanced section as a second part to the balanced circuits. — Preceding unsigned comment added by Jaredmporter (talk • contribs) 22:38, 27 November 2013 (UTC)[reply]

Sounds like a good idea. Minor point is to be careful of the WP:TONE...just say what it is, rather than saying that "we see" it or that something is good to note. DMacks (talk) 23:00, 27 November 2013 (UTC)[reply]

That's a neat equation-alignment feature, no? DMacks (talk) 05:23, 2 December 2013 (UTC)[reply]

yes, it is. 85.110.119.56 (talk) 06:03, 3 December 2013 (UTC)[reply]

Old discussions, some of which haven't been active in years, can be found in the talk page archives linked above. --Wtshymanski (talk) 00:40, 29 March 2014 (UTC)[reply]

Can we clear this up? It's not clear why my edit was reverted. To my knowledge, the standard electrical install required for most home-loan financing is a 200-A 2-phase system. There are other details if you look farther up the distribution network but at a residence, there are 2 phases and a neutral. So... what's the reason for the reversion? — Preceding unsigned comment added by Neffk (talk • contribs) 19:41, 5 May 2014 (UTC)[reply]

It's fed from one of the three phases of the distribution, which is converted to a split-phase. The result is two opposing phases (180°, or + vs – of same "phase"), not two of the three three-phase (120°) phases. File:Polemount-singlephase-closeup.jpg is pretty standard last hop before residence. Notice one primary-side bushing, and two secondary (plus center-tap neutral). DMacks (talk) 19:57, 5 May 2014 (UTC)[reply]

It looks like two phases, but in electric-speak it counts as one. Phases that are 180 degrees apart don't count as additional phases. I agree it is a funny rule. Note also that you could use center-tapped transformers on a three-phase wye system, and, I believe, it would still be three, and not six. I don't have any reference for that, though. Gah4 (talk) 02:19, 3 April 2015 (UTC)[reply]

The standard supply to an American home is 3-wire single-phase. It's not clear what the reference to 200A for home financing is referring to though. There are thousands of homes across the U.S. still running on 100A (or lower) services, and that really has nothing to do with financing. Some financers might balk at specific types of equipment which have been shown to have problems (e.g. some Federal Pacific panels), but that's a different matter. 97.84.107.236 (talk) 16:08, 23 November 2015 (UTC)[reply]

"While a single phase AC power supply requires two conductors (Go and Return), a three phase supply can transmit three times the power by using only one extra conductor. This means that a 50% increase in transmission cost yields a 200% increase in the power transmitted. [3]"

That depends on how the sytem is set up and under what condition power is transfered and measured. The transfer may be 3 times or squareroot(3)=1,73 times the transfer of two phase connected loads. KjellG (talk) 15:04, 28 May 2014 (UTC)[reply]

For a balanced three-phase delta system, limited by voltage to ground (dielectric breakdown) and current (thermal), the three-phase system allows three times the power. For an unbalanced system, three phase wye, or other limitation, it will be less. But then it says "can" not "always will be". The 50% increase and 200% increase are hard to read, even if correct. Gah4 (talk) 13:50, 3 April 2015 (UTC)[reply]

The principle behind this is that a 3-phase system makes optimal use of the conductors (given a maxium permissive voltage) by using all of them at the maximum permissible voltage, while single phase and corner grounded delta systems make less use of them because they have a neutral. The same may be obtained with a single phase system, it is just a matter of using both conductors at the same voltage (for instance, by grounding the center tap of a transformer). I have also reworded the paragraph so that it is clear that it is capacity what increases relative to material used. Mario Castelán Castro (talk) 18:57, 3 April 2015 (UTC).[reply]

Hello. This article and three phase are about exactly the same topic. Three phase explains the mathematics of a three phase system, but I think than that should be explained here as well, since it's a single topic. Under the relevant policy on merging I think that this is an instance of overlap. I can understand having several articles on a topic when it's very lengthy and complex, like relativity (physics) and introduction to special relativity but this is not the case here. Regards. QrTTf7fH (talk) 16:10, 4 August 2014 (UTC).[reply]

Go for it. Once you eliminate the math typesetting from three phase, there's not much content that isn't duplicated here or better off here. Wikipedia is not a textbook and showing all the derivations is a job for a textbook, not an encyclopedia. --Wtshymanski (talk) 02:50, 5 August 2014 (UTC)[reply]

As an undergraduate physics student and high-functioning autistic, these articles should be kept separate as the theory and application in the real world are quite different even though there is significant overlap. An analagous situation would be microeconomics and macroeconomics. The size and scope of the two articles here are different enough that both should be improved and contain links to each other. Another crucial point here is that physicists define electricity and mathematically treat it from a different perspective as electrical engineers. Interestingly, the first comment above mentions both special relativity and general relativity and from the perspective of the most general audience, certainly two separate articles are more than justified. Possibly the two articles could/should be merged but not until the content is both improved and simplified as to complexity so the general reader level is at least as supported as the electrical engineer reader. Cheers. Gf1422 (talk) 08:41, 1 September 2014 (UTC)[reply]

Hello, I think it is very badly written and is confusing. — Preceding unsigned comment added by 202.6.136.224 (talk) 06:01, 10 February 2015 (UTC)[reply]

I think they work well separate. Very litle math is required to actually use three phase power, mostly knowing where to put the square roots of three. I am sure that the people who string up long distance power lines don't do much of the math. If one does want the math, there is a place to find it. Gah4 (talk) 00:58, 14 May 2015 (UTC)[reply]

Oppose This merger proposal has been up since August of 2014, and though there has been little discussion here, it is obvious that there is no consensus. My personal opinion is that Three Phase should be its own article, as it is its own mathematical and physical concept and deserves its own discussion. Meanwhile, the three-phase electric power article also should be its own article, as it is the most widely used form of electricity distribution in the world. Since this proposal has been up for a very long time, and there is not consensus, and it has been sparsely discussed for several months, I think this fits the description of a failed merger proposal (see Step 4 on that page), so I'm removing the merger tag from the article. If anyone strongly disagrees, please start a new discussion! Spiral5800 (talk) 17:34, 23 June 2015 (UTC)[reply]

Suggest the reference to IEC 60446 is cleared and the correct reference to IEC 60445 is put in (change since 2010), this is regarding color coding of wires Sigurdurs (talk) 09:27, 29 April 2015 (UTC)[reply]

Done, but I have left the link to 60446 in place since that page has the information. IEC 60445 is currently just a redirect to List of IEC standards. SpinningSpark 15:44, 29 April 2015 (UTC)[reply]

There is a comparison of three phase delta with one phase, hot and neutral, in power transmission efficiency. It would seem more fair to compare to two-wire single phase with grounded center tap. Also, is phase-to-phase voltage a more useful comparison than phase-to-ground? Gah4 (talk) 21:00, 13 May 2015 (UTC)[reply]

I don't understand why you want to compare to the rather unusual single-phase centre-tapped (split phase). The comparison between single-phase two-wire and three-phase three-wire on a power per conductor basis seems perfectly valid to me. On the phase-phase voltage issue, the limiting factor on overhead lines is likely the voltage across the insulators between the lines and the pylon, that is, the phase to earth voltage. The phase to phase voltage may be significant in an underground cable however. In any case, my purpose in the edit under discussion was simply to restore a reference which properly verifies the text in the article, not to try and justify the validity of the comparison. If you want to make a different comparison, you are welcome to look for a source that it can be cited to. SpinningSpark 22:18, 13 May 2015 (UTC)[reply]

If the question is the efficient transfer of power over some distance, and the restriction is phase to ground voltage, then I see no reason why one wouldn't minimize the phase to ground voltage by using a center tapped transformer. On the other hand, if you do want to compare phase and neutral, a fair comparison might be to three phase wye. As far as I know, in the case of one phase to neutral, it is usual to use earth ground return, which also saves on wire cost. You are probably right about insulators being the limit, though at some point corona discharge off the wires becomes important. Gah4 (talk) 00:50, 14 May 2015 (UTC)[reply]

To be sure that my comment wasn't confusing, I said two-wire with grounded center tap. If you want to minimize phase to ground voltage and maximize phase to phase voltage, you have to ground the center tap of single phase and three phase. Not allowing for the optimal system for both cases is pretty much the same as the old 'one hand tied behind your back' restriction. Gah4 (talk) 07:20, 11 December 2015 (UTC)[reply]

I chose to add some extra information about high phase order systems dealing with the pros and cons of why they could be practical but aren’t. In addition, I wanted to make it clear that while 6 or 12 phase systems are indeed more efficient, there are clear drawbacks that make it impractical today. If accepted, this should go in the last bullet point under 'Alternatives to three-phase'.

Please change

Bulletpoint under 'Alternative to three-phase' should change from:

• High-phase-order systems for power transmission have been built and tested. Such transmission lines typically would use six phases or twelve phases. High-phase-order transmission lines allow transfer of slightly less than proportionately higher power through a given volume without the expense of a high-voltage direct current (HVDC) converter at each end of the line. However, they require correspondingly more pieces of equipment.

to the following:

• High-phase-order systems for power transmission have been built and tested. Such transmission lines typically would use six phases or twelve phases in order to maintain both the cancellation of triplen harmonics and forgoing the need for a neutral wire for return. Higher-phase-order systems provide more efficiency and smoother power transfer. High-phase-order transmission lines allow transfer of slightly less than proportionately higher power through a given volume without the expense of a high-voltage direct current (HVDC) converter at each end of the line. However, with these benefits come issues of cost, equipment, and analysis. Higher phases require an increased number of buses and conductors, in addition to to more power transmission lines. These lines also need to be transposed significantly with one another-for example, a six phase power system would need to transpose the line a total of six times to maintain balance. Analyzing a system with higher phase is also much more complex than a three phase network; therefore, maintenance of a higher order system is more difficult to comprehend. Additionally, the increase in efficiency of one phase to three phase power is much more significant than the increase in efficiency of three phase to a higher phase; as a result, it is at three phase power that we find the optimal amount of power efficiency for cost. It is also important to note that there are little to no advantages for a four or five phase power system compared to a three phase system as these systems are unable to deliver constant power; therefore, only higher order n-phase systems that are multiples of three should be considered as being advantageous to the conventional three phase system. ^[1]

Sidd26 (talk) 21:39, 9 December 2015 (UTC)Sidd26[reply]

Sidd26 (talk) 03:05, 9 December 2015 (UTC)[reply]

• Not done: please provide reliable sources that support the change you want to be made. Every claim must have a source that can be used to verify that information. --Stabila711 (talk) 03:09, 9 December 2015 (UTC)[reply]
• If you actually clicked on the link in my response you would realize that YouTube is not acceptable. It is not a reliable source and it cannot be used. --Stabila711 (talk) 01:17, 10 December 2015 (UTC)[reply]

A center-tapped one phase system isn't called two-phase even though the phases are 180 degrees apart. This makes sense. So, what is a six-phase system? Is it a three-phase system, adding lines 180 degrees from each phase? Seems like according to the counting system, that is still three phase. It may, however, in some cases be useful, and is easily to interface with three-phase systems. So, six phase should be 12 wires, and 12 phase should be 24 wires. These won't be easy to interface with the rest of the grid, and are unnecessarily complicated. Gah4 (talk) 07:41, 11 December 2015 (UTC)[reply]

I was about to ask this question again, but I see no comment since I asked last. Anyone want to comment on it? Gah4 (talk) 23:43, 27 July 2016 (UTC)[reply]

Unbalanced loads When the currents on the three live wires of a three-phase system are not equal or are not at an exact 120° phase angle, the power loss is greater than for a perfectly balanced system. Current unbalance can be caused by a number of things. One possible instance is unequal distribution of a single-phase load, which can occur if low voltage single-phase services are connected to the phase closest to neutral. Current unbalance is the primary cause of voltage unbalance, which increases heating losses in three-phase motors and negatively affects the torque and speed of the motor. The method of symmetrical components is used to analyze unbalanced systems. Wye For the wye case, all loads see their respective line voltages, and so:[12]

where Ztotal is the sum of line and load impedances (Ztotal = ZLN + ZY), and θ is the phase of the total impedance (Ztotal). The phase angle difference between voltage and current of each phase is not necessarily 0 and is dependent on the type of load impedance, Zy. Inductive and capacitive loads will cause current to either lag or lead the voltage. However, the relative phase angle between each pair of lines (1 to 2, 2 to 3,and 3 to 1) will still be −120°. In a wye connection, the phase voltages are equal to the line-to-neutral voltages (Va, Vb, Vc) and the phase currents are equal to the line currents (Ia, Ib, Ic). The wye connection can be analyzed through a one-line diagram. By applying Kirchhoff's current law (KCL) to the neutral node, the three phase currents sum to the total current in the neutral line. In the balanced case:

And in the one-line diagram: Ia = Va / ( Zline + ZY) , Ib = Vb / ( Zline + ZY) , and Ic = Vc / ( Zline + ZY) Delta In the delta circuit, loads are connected across the lines, and so loads see line-to-line voltages:[12]

Further:

where θ is the phase of delta impedance (ZΔ). Relative angles are preserved, so I31 lags I23 lags I12 by 120°. Calculating line currents by using KCL at each delta node gives:

and similarly for each other line:

where, again, θ is the phase of delta impedance (ZΔ). In a delta connection, phase voltages are equal to the line voltages (Vab, Vbc, Vca) and the phase currents are equal to the current line to line (Iab, Ibc, Ica). Neutral is not present in a delta connection.

Jgeffrey (talk) 21:49, 9 December 2015 (UTC)Justin Geffrey Jgeffrey (talk) 21:49, 9 December 2015 (UTC)[reply]

• Not done: please provide reliable sources that support the change you want to be made. --Stabila711 (talk) 01:17, 10 December 2015 (UTC)[reply]

For high voltage transmission systems, it is usually close enough to balanced. With a large number of loads, it is unlikely that it would be so far off. For a single branch circuit, maybe not so unlikely, but also not a big problem. Just be sure to use big enough wire. Gah4 (talk) 07:33, 11 December 2015 (UTC)[reply]

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I put a ^{[citation needed]} in for staggering the phases in Germany, and that the first phase has more load. I suppose it makes some sense, but still isn't so obvious. Panels I know of cycle the phases going down, and I don't see so much reason to put a higher load in the first, fourth, seventh, etc, positions. Enquiring minds want to know. Gah4 (talk) 23:58, 27 September 2016 (UTC)[reply]

I propose that Phase sequence be merged into Three-phase electric power, because the section Three-phase_electric_power#Color_codes in effect discusses sequence. Comfr (talk) 19:02, 14 October 2016 (UTC)[reply]

And then redirect to that section. Sounds right to me. Why does Phase sequence exist at all? Gah4 (talk) 20:25, 14 October 2016 (UTC)[reply]

I put in a redirect at Phase sequence but on re-reading the section here, there was no need to merge in that text - it's lucidly described here and with a reason why it matters. --Wtshymanski (talk) 17:10, 17 January 2017 (UTC)[reply]

I don't like this article. I don't think it's well written. It's rather sloppy, unorganized and I think it should be revised. In particular, I don't like the way it's split into sections. I have a series of comments.ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

1. The sentence “The three-phase system was independently invented by Galileo Ferraris, Mikhail Dolivo-Dobrovolsky, Jonas Wenström and Nikola Tesla in the late 1880s.” is contradicting the sentence found in the Polyphase system article which says “Induction motors using a rotating magnetic field were independently invented by Galileo Ferraris and Nikola Tesla and developed in a three-phase form by Mikhail Dolivo-Dobrovolsky in 1889.” The two should be consistent. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

I agree on this aspect. I switched to the discussion section for exactly this reason. Tesla did not invent three-phase power. His system was one and two-phase power (see Niagara hydropower station). He laid the basis, but Dobrovolsky was the mind that spotted the advantages of using three 120°-shifted phases. — Preceding unsigned comment added by 45.37.67.204 (talk) 03:34, 1 May 2017 (UTC)[reply]

2. The sentence "At the power station, transformers change the voltage from generators to a level suitable for transmission in order to minimize losses." and the sentence "After further voltage conversions in the transmission network, the voltage is finally transformed to the standard utilization before power is supplied to customers." should be combined and it would be nice to specifically say that from the power station, the voltage is stepped up for transmission and then stepped down for local distribution. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

Well, it can go up and down along the whole path, depending on the optimal voltage for each segment. I suppose in most cases, it it stepped on once, right at the source, and then down in steps, closer and closer to the end user. But that is already more than just stepped up for transmission and then stepped down for local distribution Gah4 (talk) 05:23, 6 November 2016 (UTC)[reply]

3. Sections “Transformer connections” and “Three-wire and four-wire circuits” both introduce wye and delta configurations which is redundant. Also, if the sections are merged, the "Wye (Y) and delta (Δ) circuits" image should be next to it instead of having the image to the right of the “Transformer connections” section. As of now, I would remove the image to the right of the “Transformer connections” section because I don't see any use for it. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

Many articles have duplication. Sometimes it is useful, as someone might not read the whole article. Most often, it can probably be fixed. Sometimes it comes from article merging. Gah4 (talk) 05:23, 6 November 2016 (UTC)[reply]

4. "An example of application is local distribution in Europe (and elsewhere), where each customer may be only fed from one phase and the neutral (which is common to the three phases)." If it's all over the places why say "Europe (and elsewhere)"? It sounds ridiculously unnecessary. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

As well as I know, many places in Europe distribute three phase to houses. Not so unusual in industrial buildings, even apartments and dormitories in the US, but pretty much never to single family houses. Gah4 (talk) 05:23, 6 November 2016 (UTC)[reply]

5. The caption for the “high-leg delta image” is like a poem. Add the information in the article instead. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

6. "However, since those references appeared homes in Europe and the UK have standardized on a supply with a nominal 230 V between any phase and ground". This sentence is not properly written and needs to be fixed. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

If you see an individual sentence that needs fixing, just fix it. Others will change it again, if needed. For bigger changes, discussing it here is probably best. Gah4 (talk) 05:23, 6 November 2016 (UTC)[reply]

7. "Separated it from another common method, the static converter, as both methods have no moving parts, which separates them from the rotary converters." This sentence is not properly written and needs to be fixed. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

8. "new work" and "old work" ... what is that? Please explain. ICE77 (talk) 04:33, 6 November 2016 (UTC)[reply]

New work is in new buildings, old work is in existing buildings. Yes, that confused me for a while. Gah4 (talk) 05:23, 6 November 2016 (UTC)[reply]

"The three-phase system was independently invented by.... " looking up citations on this in the past what I came across is none of these people invented "three-phase", it was an obvious idea right from the start of engineering AC systems. That is why these (kinda WP:SYNTH) lists change through Wikipedia - they really only cite the people who worked with it, not who invented it... and that is quite a few engineers. Another citation notes three-phase was a great idea but a logistical nightmare, hard to implement in all the single phase systems and even DC systems that existed at the time. It was a slow roll out patched over by a "Universal System". Noticed it needed rewriting for a while. Fountains of Bryn Mawr (talk) 13:48, 6 November 2016 (UTC)[reply]

Was it really that obvious? It is hard to know now what people knew or thought at the time. It is pretty obvious when the idea of an AC induction motor comes up, but I am not sure that was so obvious at the time. I thought that two-phase (four wire) systems were built in the early AC years, before three-phase was obvious enough better, but I haven't tried to follow it so carefully. Was the original Niagra falls system two or three phase? Gah4 (talk) 20:30, 6 November 2016 (UTC)[reply]

Now you will have me hunting for references ;). "obvious" as in all the early thinkers in AC (Haselwander, Ferraris, Dolivo-Dobrovolsky, Wenström, Tesla) were on to it. 3-phase was out there before Niagara, Dolivo-Dobrovolsky perfected that in 1889, but Niagara was built by Westinghouse and they had 2-phase based Tesla patents (a second contract went to GE to build 3-phase transmission lines). The better European 3-phase systems were being kept out of America at that point by the Tesla patents (the same thing would happen again a few years latter when the Wright Brothers patents would keep European aircraft innovations out of America). At the point of Niagara it was all academia, the systems they were linking up were archaic single phase AC, DC light, DC street cars, and factories powered by DC motors or steam engines -- 2-phase or 3-phase didn't matter... the advantages of either system were a pipe dream. Fountains of Bryn Mawr (talk) 23:27, 6 November 2016 (UTC)[reply]

I've had a look at a few of the points made above. Main articles are for details, we just need to summarize here and link. People should come back the next day and read their contributions out loud to themselves - it would smooth our our style a lot. --Wtshymanski (talk) 18:30, 17 January 2017 (UTC)[reply]

In the US, you pretty much never see three phase in single family homes. It isn't so unusual for apartments or dormitories, though. But as I understand, it is usual in some countries in Europe, and maybe elsewhere. Are there any sources on which countries? Gah4 (talk) 22:44, 10 November 2016 (UTC)[reply]

My experience in Australia is vaguely relevant. My family lived in a house that, like most others, was served by a single phase. Then my mother bought a new oven that operated on the higher voltage only available with two phases. The oven was installed and the second phase was brought to the house and everyone lived happily ever after. Dolphin (t) 11:00, 11 November 2016 (UTC)[reply]

There seems to be disagreement on a paragraph about the efficiency of 3 phase, and even the meaning of the quoted source. I reverted to keep the paragraph out until this can be straightened out. I believe that there have been questions about this in the past, but that it never got really resolved. It is now time to finally get it right, one way or the other. Gah4 (talk) 05:57, 16 September 2017 (UTC)[reply]

It's pretty commonly accepted - you can put 1.7 times the power through a set of 3 wires energized at the same voltage to ground as you can through 2 wires, so you get 1.7 timest eh pwoer for 1.5 times the weight of conductor. "American Electrician's Handbook, 11th edition" gives a table comparing the several systems on page 3-10, which also shows that a 3-phase 3 wire system needs 87 % of the copper of a 2-wire circuit for a given power transmission capacity (at the same voltage to ground). --Wtshymanski (talk) 17:31, 16 September 2017 (UTC)[reply]

The problem with your analogy is that as soon as you use all three phases to power anything, you lose the argument that it's more efficient because of the simple fact that you're using at least one extra conductor to do the work. Amperage (in other words "load", or the work the wire is doing) is a function of Voltage not phasing. Phasing is not used for that reason. Phasing is primarily used for large industrial motors because it allows them to run more efficiently, but not because you're breaking up the load - because of the lack of the sine wave ever hitting a zero point like it does in single phase. This is the reason you don't see 3 phase power to residential homes... it's impractical and unnecessary. Ask yourself this question... if three phase power is a more efficient means of transmission, why is it not used in residential homes, or in other words - 80% of the end users the power company supplies? The answer is simple. It's in NO WAY more efficient than single phase. Not trying to sound arrogant, but I've been a master electrician for 20+ years and I know you probably don't completely understand. If you were in front of me, I could draw a simple diagram to show what three phase is, vs what single phase is and why you're thinking about this all wrong. "Three phase" is a reference to the way power is generated, and not the way power is transmitted. Voltage is the way power is transmitted. Simply put, one leg of a three phase system at 120 volts (or ANY voltage) can not do any more work than one leg of a single phase system at the same voltage. — Preceding unsigned comment added by 72.74.147.209 (talk) 00:07, 17 September 2017 (UTC)[reply]

And I'd like to add that I absolutely DO understand the math and theory behind the efficiency of three phase distribution and why it's better than single phase for that purpose, I will quote specifically from the deleted section what is wrong and misleading...

"A three-phase system is usually more economical than an equivalent Single-phase electric power single-phase circuit at the same line to ground voltage because it uses less conductor material to transmit a given amount of electrical power."

Line to ground, there simply is no difference in efficiency. Its a gross over-simplification of a very complicated subject, and misleading to the reader. That's not where the efficiency of three phase distribution is derived. That section is poorly written and leaves the reader thinking, "then why isn't it used everywhere for everything?". Its explained much better in the Advantages section, so even having it is redundant anyway. — Preceding unsigned comment added by 72.74.147.209 (talk) 00:57, 17 September 2017 (UTC)[reply]

The claim in the article is sourced to a reliable source. If you wish to claim the opposite, then you need to produce a source that is better than the one provided to support your argument. You have so far failed to do so.

Three-phase power is used in residential homes in some countries in the world precisely because of the economies in copper usage gained (Germany immediately springs to mind where most domestic cookers are supplied with 380/220 volts three phase). Most systems only supply single phase to homes because the loads are not large enough to provide significant benefit. But even so, nearly all residential homes are supplied using three-phase distribution, with every third house being fed from the same phase (again because of the economies to be gained become worthwhile). Aircraft almost exclusively use three-phase distribution because of the significant weight savings (and on aircraft unnecessary weight means unnecessary fuel consumption).

I suggest that you read the reference given and try to understand it, rather than trying to claim that you are 'master electrician'. Wtshymanski (or W.T. Shymanski^[1]), who keeps reverting you, is a fully qualified professional electrical engineer (look him up on line), so should know something about the subject. 86.168.83.171 (talk) 11:43, 17 September 2017 (UTC)[reply]

The article mentions one specific case, which is three phase wye vs. one phase, either phase to ground or split (center tapped) phase. That is commonly used for the last few hundred feet. But long distance power transmission is three phase delta, pretty much always. Three phase delta is just as efficient, line to ground, as one phase with two wires with the same line to ground voltage. It takes very little vector arithmetic to see that, and most of it is shown on the linked page. The statement in question doesn't distinguish these cases, implying that in all cases three phase is more efficient. Even more, all these comparisons are for unity power factor linear loads. The math gets more complicated with other types of loads. One interesting case occurs with three phase wye and discharge lamps, which are a non-linear load. With three phase wye and linear loads, it isn't hard to see that the neutral current is never more than the largest phase current. That turns out not to be true for non-linear loads, where the third harmonics add. It also gets more complicated with inductive loads, where the current and voltage are not in phase. But the statement in question does not leave any indication that there are other cases in question. One that is true, though, is that once you go to single phase, you can't get three phase back again. The most important case for three phase is induction motors, and is important enough to want to keep three phase, even when the transmission efficiencies are equal. Gah4 (talk) 11:52, 17 September 2017 (UTC)[reply]

Three phase to single family residences is pretty rare in the US. One reason is that most large current appliances are designed for 240V and not 208V. 208/120 wye is common in industrial and often in apartments and dormitory buildings. (Ovens, stoves, and electric dryers are usually rated for 208, at a lower power.) For single family homes, though, it is usual to run only a small number of houses off one transformer. The complication of a three phase transformer, for such a small number of houses, is not economical. European 380/220 is distributed to more houses, per three phase transformer, enough to make up for the transformer cost. That is partly due to the smaller wire size needed for 380/220 vs. 208/120. But power distribution efficiency is pretty much determined by the hundreds of miles of long distance transmission, and not the hundred feet (30m) to individual houses. Gah4 (talk) 12:10, 17 September 2017 (UTC)[reply]

The problem with the statement in question isn't that it is right or wrong, but that it is too general, but doesn't give any indication that it is too general. Gah4 (talk) 12:10, 17 September 2017 (UTC)[reply]

• There are any number of good sources to support the efficiency claims for 3 phase. There is no reason to doubt any of this. If the anon IP wants to contradict them, then the onus is on them to provide good, independent reliable sources, not opinions, as to why. Andy Dingley (talk) 13:57, 17 September 2017 (UTC)[reply]

Arguments about "efficiency" usually revolve around what you choose to define as "efficiency". A three-phase, three-wire system uses less mass of copper to transfer a given amount of power than a two-wire single phase system; alternatively, since wires come in gauge sizes, a given gauge of wire used in a 3 phase 3 wire system will transfer 15% more power per unit weight of copper. Generally, the cost of a wiring system is proportional to the mass of conductor used, though practicalities intervene at every step. --Wtshymanski (talk) 01:44, 18 September 2017 (UTC)[reply]

By way of illustration only, if you had to transmit 100 kw single-phase, you would have a circuit current of 500 amperes. Usin ghte standard values from Table 1 of the Canadian Electrical Code and assuming 200 degrees C maximum conductor temperature, this would need 2 conductors of 4/0 AWG, a total mass of about 61.6 stone per furlong. If you used 2 phase also at 200 volts to ground, you would need 3 wires carrying 289 amps, which Table 1 says you can put over a bare wire at 200 C of #1 AWG size; three of those would mass 36.5 stone per furlong. If you used an Edison split-phase circuit and ran each leg at 200 volts to ground, and provided a full-size neutral, you'd need 3 conductors - the outer two would be carrying 250 amps, the neutral would carry 0 amps, and Table 1 says you'd need 3 conductors, also #1 AWG at 200 C, massing again 36.5 stone per furlong. So, a 3 phase circuit uses less copper than a single-phase 2 wire circuit, and the advantage of the split-phase circuit is apparent, making the initial electric lights a rich man's plaything instead of a laboratory curiosity. The weights don't scale exactly as sqrt(3)*2/3 because of the granulation of wire sizes, and of course no-one designs a circuit around 200 C temperature conductors (but it's in the code?). --Wtshymanski (talk) 02:51, 18 September 2017 (UTC)[reply]

It seems to me that the reason for all the confusion is that some are considering three phase delta, and others three phase wye. The reference given compares three phase wye to two wire and three wire systems with a neutral. I now updated the article to state what the reference is comparing. It is not hard to see that, for a given line to neutral voltage, three phase delta (with no neutral), and one phase, two wire (again with no neutral) are equally efficient in power per wire. Comparing three phase delta line to line with a two wire, one phase, system with the same line to line voltage, the three phase delta is a little more efficient, but the cited reference doesn't cover this at all. Line to ground is probably a better comparison, as that depends on insulator strength and such. Gah4 (talk) 04:14, 18 September 2017 (UTC)[reply]

Whether the load is a delta connected or wye connected is irrelevant. The power conveyed by the system is (3*phase voltage*phase current*cos phi) in both cases. For the wye system, phase voltage is the voltage between any phase and neutral (or the star point of the load if no neutral is provided) and phase current (which is also the line current) in each phase. For the delta connected load, phase voltage is the voltage between two phases (and is also the line voltage) and phase current is the current through each side of the delta load (and equals the square root of 3 times the line current). For the purposes of measuring the power carried by the system, the connection of the load (wye or delta) is irrelevant (and any connected three-phase wattmeter would be unaware of it anyway).

For a balanced wye load, it is unnecessary to provide a neutral conductor as it carries no current and providing it partially negates the copper saving that the three-phase system affords. For three-phase distribution used for supplying unbalanced loads, the neutral must be provided (and it thus always carries some current). Global wiring codes used to vary in its sizing, but in the UK, the neutral used to be specified to carry half the line current. The invention of fluorescent lighting changed everything because such lighting draws current with a significant third harmonic. The problem is that all the third harmonic currents in each phase are all in phase and thus all flowed through the neutral (which thus carries the sum of the third harmonic current in each phase). Consequentially neutral conductors are now universally specified to be the same size as the phase conductors. 86.168.83.236 (talk) 13:03, 18 September 2017 (UTC)[reply]

It's reassuring to see that the 'farthing, fathom, fortnight' system of units isn't dead! 86.168.83.236 (talk) 13:10, 18 September 2017 (UTC)[reply]

The advantage of split phase (center tapped one phase) is that it shares the neutral with two circuits, even if you don't have line to line loads. I have seen house wiring that runs three wires down a wall with two circuits. I believe this is still legal in the US NEC, but you can't run the neutral through an outlet. Three phase wye shares the neutral among three phases. Yes with balanced linear loads, there is no current in the neutral, but you can't guarantee that. Someone might turn a lamp on or off. With unbalanced linear loads, the neutral current is never more than the maximum phase current. Note that this doesn't continue. With a five wire, two phase, system, with appropriate unbalanced loads, the neutral current can be more than the phase current. And if you read the reference, this is exactly the case described. It is the sharing of the neutral among two (split phase) and then three (wye) that gives the advantage. On the other hand, it doesn't take much math to see that three phase delta, line to ground, is just as efficient as one phase, also without neutral, line to ground, at the same line to ground voltage. But if you don't distribute three phase, then you can't have three phase wye at the end. (Note that with non-linear loads, three phase wye can have more neutral current than phase current. This case is well known, putting gas discharge lamps on poles, balanced across the phases. Third harmonics add in phase.) Gah4 (talk) 17:43, 18 September 2017 (UTC)[reply]

The reference discusses three-phase wye circuits without the star points of the voltage sources or the loads connected together (i.e. without a neutral). It mentions that adding a neutral can solve a few problems in the case of faults or failure. This is discussed later in the article but not in the lede. However, for normal operation, the neutral is clearly shown as carrying zero current. That means that for circuit analysis purposes it matters not one jot whether it is there or not. The reference does not discuss unbalanced three-phase circuits at all so your continued reinsertion of 'four wire' in that context in the article is not supported by the reference. It takes little maths to see that the delta and wye case makes no difference all to the analysis (as I have detailed above) so your assertion here is incorrect. Three phase power =3*phase current*phase voltage*cos phi in both cases and does not change between delta and wye. 86.168.83.236 (talk) 17:53, 18 September 2017 (UTC)[reply]

Are you reading the same reference that I am?^[1] All the examples have a neutral. It starts with one phase, then split (120/240), and then two phases (120/208) 120 degrees apart, still with a neutral. It does mention balanced three phase has no neutral current, but just as important unbalanced can never be more than any phase current. As you note: three phase power =3*phase current*phase voltage*cos phi In the case of single phase two wire without a neutral, the power is 2*phase current*phase voltage*cos phi, for the same power per wire and voltage to ground. Using the same math, you can show that for N phases and N wires (N>1) equally spaced in phase, that the power is N*phase current*phase voltage*cos phi. As N increases, the phase to phase voltage decreases, which might be an advantage. But the reference doesn't discuss that at all. It is the sharing of the neutral that is the advantage, just as the article says. Gah4 (talk) 19:08, 18 September 2017 (UTC)[reply]

Yes, I am reading the same reference that you are. You seem to be mentally conjuring neutrals where none exist. Ignoring the first two diagrams which are not three-phase systems, diagram three has no neutral connection and neither does diagram four, both of which illustrate the analysis of the circuit. Diagram five is supposed to be diagram four annotated with the SPICE results but for some reason has added a neutral connection (though it is annotated as carrying no current so is entirely superfluous - though the reference mentions its use in connection with fault tolerance though real world systems do not always provide the neutral)

You do seem to have missed the whole advantage of the three-phase system. If you go back to the first two diagrams, 83.33 Amps are flowing in the two line conductors and the neutral conductor for a total delivered power of 20 kW. That requires three conductors sized to carry the 83.33 Amps. The reference also (correctly) notes there is no gain over the split phase system because three conductors rated at 83.33 Amps are required there as well. The split phase provides a gain over a true single phase system because a 20 kW load requires two conductors rated to carry 166.6 Amps (i.e. 33% more copper - or alternatively, the split phase system uses 50% less copper for the same load).

For the three-phase system, you now have 3 x 10 kW loads using 3 conductors rated to carry 83.3 Amps. That is 33.3% more power for the same amount of copper. Alternatively, if you re-rated the three loads to 6.666 kW each that would be the same transmitted power as the split phase case but requiring 33.3% less copper to carry the 27.7 Amps per phase. This also works out as 25% of the copper required for the pure single-phase system. Thus the three phase system provides a net saving in copper over the other two system. If the neutral were to be provided the advantage over the split phase system is gone but there is still an 33.3% advantage over a pure single-phase system. 86.168.83.236 (talk) 13:01, 19 September 2017 (UTC)[reply]

It seems that there aren't numbers on the figures, but the first two have the word "neutral" on them. Three and four don't, but assume a perfectly balanced system. They explicitly say 120/208. They are used to show the need for a neutral, as you can't depend on balance. Someone might turn something on or off, and the voltage would change, when it was no longer balanced. So, in the fifth, the neutral is added. You can't have three phase wye without a neutral, unless you can guarantee balance. Gah4 (talk) 13:47, 19 September 2017 (UTC)[reply]

The first two figures are not three-phase systems, so what is your point?. Where is it written that you cannot have a three phase wye system without the neutral? It happens frequently, particularly in power distribution. If the three legs of the wye are exactly the same, then balance is guaranteed and no neutral is required. Of course, fault conditions can unbalance the system, but that can equally happen to a delta connected load where there is no neutral. Indeed, the same fault causes the wye system and its delta equivalent to behave exactly the same way because every linear wye system can be replaced by an equivalent linear delta system (and vice versa). So much so, that if I gave you a box with three terminals on it, it is impossible (short of X-raying the thing) to determine if the circuit inside is connected in wye or delta. 86.168.83.236 (talk) 14:03, 19 September 2017 (UTC)[reply]

Yes you can use a wye system as delta. As I understand it, though I don't see it in the article, it is usual to wind the secondaries of transformers as wye, even if the center is not brought out. That avoids the circulating currents that you get in a delta winding if it isn't perfectly symmetric. But for an actual wye system, with loads from phase to neutral, as the reference uses, you need the neutral, unless you can otherwise guarantee balance. You could, for example, wire a motor as wye, and not bring out the center. But you can't connect light bulbs, with their own switch, from phase to a non-existent neutral, as turning one on or off will unbalance the system. As it says in the reference: To ensure load voltage stability in the event of another load opening, we need a neutral wire to connect the source node and load node together. Gah4 (talk) 14:29, 19 September 2017 (UTC)[reply]

Hang on a mo. You are moving the goal posts. You are now talking about unbalanced systems using single phase loads between any phase and neutral. That is not what is being discussed and not what the reference addresses. The phrase you quote, in its context, is addressing fault conditions (the use of the word, "fail" in the previous sentence is a clue here). Neither the diagram nor the text makes any indication that it is addressing a deliberately unbalanced system. The neutral is not necessarily 'need'ed as the reference suggests, a lot depends on how fault tolerant the system is.

Whilst it is true that alternators and secondaries of transformers are connected in wye (for the reasons that you state), motors and transformer primaries are generally delta connected to avoid the expense of having to provide an otherwise unnecessary bonding point for the star point. There would be no point bringing the neutral out from the supplying transformer/alternator for such a balanced load and indeed they rarely are. I believe that you are trying to synthesise something out of the reference that is not there to support your edit. 86.168.83.236 (talk) 16:18, 19 September 2017 (UTC)[reply]

It seems to be the way the reference is written. The load opening case is someone turning on or off a switch. Yes it could have been explained better, and yes I could find more quotes. I could say it the other way, that you are trying to synthesise something out of the reference that is not there to support your edit. The whole reference is on 120V loads connected in various ways. There are no delta connected loads, and wye isn't wye without a neutral. As you note, you can connect delta loads to a wye system, but that doesn't make it a wye load, or delta source. The source does mention line to line voltage for safety reasons, but not for loads. A later quote: When we contrast these two examples against our three-phase system (Figure above), the advantages are quite clear. First, the conductor currents are quite a bit less (83.33 amps versus 125 or 250 amps), permitting the use of much thinner and lighter wire. We can use number 4 gauge wire at about 125 pounds per thousand feet, which will total 500 pounds (four runs of 1000 feet each) for our example circuit. See where it says four runs, and not three? Gah4 (talk) 19:48, 19 September 2017 (UTC)[reply]

It would be nice to have a reference on transformer connections. As noted, you want transformer secondaries to be wye, even for delta loads, to avoid circulating currents. A wye secondary and delta primary means a 60 degree phase rotation, which may or may not be a problem. Gah4 (talk) 19:48, 19 September 2017 (UTC)[reply]

Are there any other references in the world that explain this? I haven't found any. Many explain the advantage of three phase induction motors, but ones that explain transmission efficiency are rare. Gah4 (talk) 19:48, 19 September 2017 (UTC)[reply]

A new source has been provided by another user. I don't have access to it, but given how poorly the original was presented, I have no doubt that it is better. How do you come to the conclusion that wye is not wye without a neutral? Wye is wye whether the neutral is connected or not. I cannot speak for every territory, but here in the UK, distribution transformers are invariably delta/wye (or delta/star as we call it here) so a 60 degree shift is probably

not a problem. Of course, when a second such transformer follows the first the shift disappears. 86.168.83.236 (talk) 12:05, 20 September 2017 (UTC)[reply]

It seems that the reference now uses an book not freely available, but that an older edition^[1] is out of copyright, and available. Can someone find the page with the equivalent explanation in this one? Gah4 (talk) 21:10, 19 September 2017 (UTC)[reply]

Since you are the one who found the online version of the book, what is stopping you from finding the explanation? If you are still attempting to challenge the claim, the burden is on you to disprove it (as it has already been proven by two cites which must be accepted as provided in good faith).

For your education, Fig 31 of that not very well scanned book shows a wye circuit without a neutral. 86.168.83.236 (talk) 12:44, 20 September 2017 (UTC)[reply]