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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)
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)
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)
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)
"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)
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)
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).
I still find the 'Advantages' section misleading. The first sentence touts a 3x power increase which is not an apples-to-apples comparison; the single-phase line has one hand tied behind its back (one wire is neutral, whereas all wires are hot in 3-phase 3-wire). Some people have the impression that the mighty 3x improvement is a key reason why long-distance high voltage is 3-phase rather than single; they have heard the 3x figure and don't realize that 3-wire 3-phase is only 1.5x the power of a single-phase line with two hot wires. Tom239 ( talk) 04:52, 13 May 2020 (UTC)
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).
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)
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)
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)
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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)
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)
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)
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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
Sidd26 (
talk) 03:05, 9 December 2015 (UTC)
References
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)
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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)
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)
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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)
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)
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)
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)
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)
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)
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)
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)
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)
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)
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)
8. "new work" and "old work" ... what is that? Please explain. ICE77 ( talk) 04:33, 6 November 2016 (UTC)
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)
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)
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)
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)
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)
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)
References
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)
References
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point 5.2.3 L1 -> black, L2 - brown, L3 -> grey — Preceding unsigned comment added by 188.84.191.124 ( talk) 12:18, 31 December 2017 (UTC)
Voltage is induced in the secondary (right coil) only when the voltage is changing in the primary Seems to me that from the way the law of induction works, a voltage is generated by a change in current. Though the current has to change appropriately to induce the right voltage. Gah4 ( talk) 19:53, 27 April 2018 (UTC)
That is, (60°). It is well known that for symmetric three-phase that the line to line voltage is sqrt(3) times the line to neutral voltage. There are plenty of sqrt(3) in ratios for equilateral triangles, so that shouldn't be too surprising. The actual form that it comes out is (60°) which comes from a difference of two sines identity. Gah4 ( talk) 05:39, 6 August 2018 (UTC)
Here are the equations
You and I know that sqrt(3) came from a trig expression, but it may not be obvious to others. Constant314 ( talk) 07:46, 6 August 2018 (UTC)
I was going to say that yours was wrong, but then I saw the minus sign. I think that makes it -60 degrees, though. The identity is sin(A)-sin(B)=2*cos((A+B)/2)*sin((A-B)/2) Gah4 ( talk) 04:41, 12 August 2018 (UTC)
Three phase submersible pumps in the USA use black/yellow/red/green wires. Black, yellow and red are for phase wires and, of course, green for the ground. Can the graphic showing wire colors for different countries be updated in the USA section to include this this? — Preceding unsigned comment added by 139.60.72.244 ( talk) 06:20, 12 August 2020 (UTC)
In the above section there is discussion on phase order, and how people get it right. It seems that there are tools, some simple, some complicated and expensive, to indicate phase, such as these. The page indicates a simple one with a capacitor, two neon lamps and current limiting resistors. Seem more obvious than spending hundreds of dollars for one. It does seem that black-red-blue is popular, but do any sites, such as NEMA, mention this? As above, the only thing that UL says, specifically about pump motors, is not white, gray, or green. It seems that a popular way to start a large (maybe 10HP) motor is first as wye, then as delta. But once you get one right, the other will also be right. Gah4 ( talk) 22:42, 16 August 2020 (UTC)
It is my understanding that it is rare to use the delta configuration for transformer secondaries. If the three transformers are not quite close enough, you can get a current around the loop, wasteful and cause of extra heating. Since you can ignore the neutral wire with wye, you can easily make a delta connection to a wye transformer, but there will be a 30 degree phase shift if the primary is delta. I suspect that connecting two transformers in parallel also has this problem. For the pump motors, the instructions I look at all said to try it and see. I believe that a centrifugal pump will still pump, but less well, with the motor going the wrong way. You are supposed to test the pressure both ways. I suspect that there are systems where that is not the best way, though. Gah4 ( talk) 21:15, 18 August 2020 (UTC)
While the language of this article is American English by random choice (no objection to that), using the phonetic spelling "Wye" instead of the letter Y to name the system where the wiring is the same as the shape of the letter Y, seems to be quite an oddity, at least to those of us that learned the techniques in any other human language.
Could someone that wrote some of this existing text weigh in on why this spelling is used instead of the single letter? Jbohmdk ( talk) 22:27, 31 July 2021 (UTC)
A recent edit reverted the change to Induction motor. It seems to me that all large AC motors are induction motors, so maybe it works either way. But the big advantage of three-phase is its used with induction motors. Well, it seems that the earliest systems used four-wire two-phase, before the standard on three-phase. In any case, for the recent edit, I vote for Induction motor. Gah4 ( talk) 03:37, 16 March 2022 (UTC)
Greetings, This page could be more informative for electrical power systems engineering and research if it included sequence impedance as in symmetrical components impedance and DQO (Direct Quadrature and Zero) impedance. Most of the power systems protection engineering is done with positive, negative and zero sequence impedances these days. DQ impedances are also used for modeling, drives controls analysis, and stability analysis of power electronic systems. If you argue that these impedances should be under DQ0 transform or Fortesque transform it would be like saying that impedance belongs under complex numbers or the Fourier transform, since that is the mathematical origin. I think these impedances belong on this page because it covers the use cases of electrical impedance in its various forms. thank you. 173.66.144.197 ( talk) 02:14, 29 March 2024 (UTC)
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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)
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)
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)
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)
"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)
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)
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).
I still find the 'Advantages' section misleading. The first sentence touts a 3x power increase which is not an apples-to-apples comparison; the single-phase line has one hand tied behind its back (one wire is neutral, whereas all wires are hot in 3-phase 3-wire). Some people have the impression that the mighty 3x improvement is a key reason why long-distance high voltage is 3-phase rather than single; they have heard the 3x figure and don't realize that 3-wire 3-phase is only 1.5x the power of a single-phase line with two hot wires. Tom239 ( talk) 04:52, 13 May 2020 (UTC)
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).
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)
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)
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)
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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)
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)
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)
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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
Sidd26 (
talk) 03:05, 9 December 2015 (UTC)
References
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)
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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)
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)
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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)
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)
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)
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)
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)
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)
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)
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)
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)
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)
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)
8. "new work" and "old work" ... what is that? Please explain. ICE77 ( talk) 04:33, 6 November 2016 (UTC)
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)
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)
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)
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)
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)
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)
References
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)
References
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point 5.2.3 L1 -> black, L2 - brown, L3 -> grey — Preceding unsigned comment added by 188.84.191.124 ( talk) 12:18, 31 December 2017 (UTC)
Voltage is induced in the secondary (right coil) only when the voltage is changing in the primary Seems to me that from the way the law of induction works, a voltage is generated by a change in current. Though the current has to change appropriately to induce the right voltage. Gah4 ( talk) 19:53, 27 April 2018 (UTC)
That is, (60°). It is well known that for symmetric three-phase that the line to line voltage is sqrt(3) times the line to neutral voltage. There are plenty of sqrt(3) in ratios for equilateral triangles, so that shouldn't be too surprising. The actual form that it comes out is (60°) which comes from a difference of two sines identity. Gah4 ( talk) 05:39, 6 August 2018 (UTC)
Here are the equations
You and I know that sqrt(3) came from a trig expression, but it may not be obvious to others. Constant314 ( talk) 07:46, 6 August 2018 (UTC)
I was going to say that yours was wrong, but then I saw the minus sign. I think that makes it -60 degrees, though. The identity is sin(A)-sin(B)=2*cos((A+B)/2)*sin((A-B)/2) Gah4 ( talk) 04:41, 12 August 2018 (UTC)
Three phase submersible pumps in the USA use black/yellow/red/green wires. Black, yellow and red are for phase wires and, of course, green for the ground. Can the graphic showing wire colors for different countries be updated in the USA section to include this this? — Preceding unsigned comment added by 139.60.72.244 ( talk) 06:20, 12 August 2020 (UTC)
In the above section there is discussion on phase order, and how people get it right. It seems that there are tools, some simple, some complicated and expensive, to indicate phase, such as these. The page indicates a simple one with a capacitor, two neon lamps and current limiting resistors. Seem more obvious than spending hundreds of dollars for one. It does seem that black-red-blue is popular, but do any sites, such as NEMA, mention this? As above, the only thing that UL says, specifically about pump motors, is not white, gray, or green. It seems that a popular way to start a large (maybe 10HP) motor is first as wye, then as delta. But once you get one right, the other will also be right. Gah4 ( talk) 22:42, 16 August 2020 (UTC)
It is my understanding that it is rare to use the delta configuration for transformer secondaries. If the three transformers are not quite close enough, you can get a current around the loop, wasteful and cause of extra heating. Since you can ignore the neutral wire with wye, you can easily make a delta connection to a wye transformer, but there will be a 30 degree phase shift if the primary is delta. I suspect that connecting two transformers in parallel also has this problem. For the pump motors, the instructions I look at all said to try it and see. I believe that a centrifugal pump will still pump, but less well, with the motor going the wrong way. You are supposed to test the pressure both ways. I suspect that there are systems where that is not the best way, though. Gah4 ( talk) 21:15, 18 August 2020 (UTC)
While the language of this article is American English by random choice (no objection to that), using the phonetic spelling "Wye" instead of the letter Y to name the system where the wiring is the same as the shape of the letter Y, seems to be quite an oddity, at least to those of us that learned the techniques in any other human language.
Could someone that wrote some of this existing text weigh in on why this spelling is used instead of the single letter? Jbohmdk ( talk) 22:27, 31 July 2021 (UTC)
A recent edit reverted the change to Induction motor. It seems to me that all large AC motors are induction motors, so maybe it works either way. But the big advantage of three-phase is its used with induction motors. Well, it seems that the earliest systems used four-wire two-phase, before the standard on three-phase. In any case, for the recent edit, I vote for Induction motor. Gah4 ( talk) 03:37, 16 March 2022 (UTC)
Greetings, This page could be more informative for electrical power systems engineering and research if it included sequence impedance as in symmetrical components impedance and DQO (Direct Quadrature and Zero) impedance. Most of the power systems protection engineering is done with positive, negative and zero sequence impedances these days. DQ impedances are also used for modeling, drives controls analysis, and stability analysis of power electronic systems. If you argue that these impedances should be under DQ0 transform or Fortesque transform it would be like saying that impedance belongs under complex numbers or the Fourier transform, since that is the mathematical origin. I think these impedances belong on this page because it covers the use cases of electrical impedance in its various forms. thank you. 173.66.144.197 ( talk) 02:14, 29 March 2024 (UTC)