Talk:Polyphase system

message: Generally this article seems to be useless because it seems to claim a huge variety of polyphase power systems exist. But there are only two types of phased power systems in common use today, known as single-phase or three-phase. Split-phase can be a combination of either of these two. Two-phase is considered an antique relic and is not used anymore.
Common use:
* Single-phase electric power - Used by most high amperage American/European residential devices, 230v Amercian or 560v European
* Three-phase electric power - Used primarily for high horsepower motors, but can still be found in residential settings if a building is a large condominium or commercial skyscraper with apartments. Direct voltage is 480-volt American. 
Combination use:
* Split-phase electric power - For single-phase power, it is used by most low amperage American/European residential devives, 115v American or 230v European. For three-phase power, the voltages can be 208-volt American if 2 of the 3 phases are used for single-phase loads, and can be used as three American 120v split-phase circuits for residential/commercial/industrial applications.
Considered obsolete:
* Two-phase electric power
* 25-hertz systems (at one time trolley cars still used it)
So what are these other phase wiring designs that this article tries to suggest may exist? It's either single phase or three phase. Nobody used four-phase or five-phase, etc. Polyphase suggests that other systems than three-phase power are in use in the world today.... but if not, then why not just call it three-phase electrical power? DMahalko (talk) 00:00, 16 May 2008 (UTC)
replies: text: US (and I believe Canadian) homes use 240V center-tapped, allowing for 120V or 240V devices. As I understand it, (not living there) Europe normally distributes three-phase wye with 230V (+/- 10) phase to neutral, for (about) 400V phase-to-phase. I suspect you never find 560V in European residences or 480 in American residences. Three-phase wye 120/208 occurs in larger US residences, such as college dormitories and condominiums. Three phase 277/480 is common for US industrial lighting, where it allows for more efficient fluorescent lighting systems, and also more efficient large three-phase motors. Gah4 (talk) 21:07, 20 July 2015 (UTC)
thread_title:  Why a page for "poly"-phase, without a list of applicable poly-phases? 

message: The article says "Polyphase systems are particularly useful for transmitting power to electric motors."  It seems to me that three phase allows for efficient long distance power distribution and also works well for motors, not necessarily both at the same time.  Gah4 (talk) 12:36, 15 November 2009 (UTC)
thread_title:  Efficiency 

message: "A polyphase system must provide a defined direction of phase rotation, so mirror image voltages do not count towards the phase order. A 3-wire system with two phase conductors 180 degrees apart is still only single phase. Such systems are sometimes described as split-phase."  I do understand not counting phases that are 180 degrees apart. It comes naturally from transformer winding physics. But why is this related to direction of rotation? Also, in describing rectifiers, the article mentions six phases. Seems like if you use the same phase counting method it should still be three, but rectifier configurations that uses six diodes. One is the three-phase extension of the usual center-tap full-wave rectifier, another the extension of the normal bridge rectifier. Is there a proper name for these rectifiers? Gah4 (talk) 20:56, 20 July 2015 (UTC)
replies: text: Continuing the question, as new additions have been made regarding six-phase, it seems to me that it is common to use a six phase rectifier on three phase power. That is, a full wave rectifier has twice the number of phases of its input source.  Does Brookhaven have a six phase input, and use a 12 phase rectifier? Gah4 (talk) 08:49, 26 December 2015 (UTC)
thread_title:  Counting phases 

message: I found this webpage http://www.thecoffeebrewers.com/electricity.html describes polyphase better than this wiki.
Haimiyahya (talk) 16:23, 3 August 2015 (UTC)
replies: text: Interesting, though most of what it says is close to right, but not quite right. For one, real generators never look like the diagram shown, which is also shown in many physics books.  It is right in theory, but in reality you need an iron core, and that completely changes the way it works, though in the end the result is the same sinusoid. For another, generators never rotate at 60Hz (3600RPM).  The usual large power generators run at 72RPM. That is, they have 100 poles instead of two.  Next, it indicates that power distributed through a neighborhood isn't in the tens of kV. I do know that the distribution through the neighborhood where I grew up was changed from 2.3kV to 22kV in about 1970.  I believe 22kV is still commonly used for residential delivery.  Next, 50Hz appliances with transformers should not have any problem at 60Hz, but not all 60Hz transformers will run properly at 50Hz.  Most likely they will, though. Next, it indicates that the usual US/Canada home power is two phase. The way electricians count, it is still single phase. That is, you don't separately count phases that are opposite sides of a center tapped transformer.  If you tell the electrician that you have, or want, two phase power, he/she will be very confused. Also, circuit breakers should be able to run at their specified current rating. Not that you shouldn't leave some margin, but if it trips at exactly the specified current, it is defective. Since the target audience is interesting in heating appliances, much of the bottom half is appropriate for that case, but not quite right for other types of loads. Next, heaters, light bulbs, and wiring works on RMS current, not peak current. The heat capacity is large enough to average out the power, such that instantaneous power isn't important, but average power is.  (At least over a 50Hz or 60Hz cycle.) The important point is almost lost in the discussion: if you run at 240V heating appliance at 208V, as is commonly done for ovens, stoves, water heaters, and clothes dryers, the power output will be reduced by about (240/208) squared. Nameplates on appliances commonly give ratings for both common power sources. A small autotransformer will get you from 208V to 230V or 240V if you want one. Gah4 (talk) 09:37, 26 December 2015 (UTC)
thread_title: Describes polyphase better

message: I don't like the introduction. The initial description/explanation is not good. It really shouldn't be so hard to come up with a clear statement.
The sentence “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.” is contradicting the sentence found in the Three-phase electric power article which says “The three-phase system was independently invented by Galileo Ferraris, Mikhail Dolivo-Dobrovolsky, Jonas Wenström and Nikola Tesla in the late 1880s.” The two should be consistent.
In my opinion the motors section should directly follow the introduction and state clearly what's the relationship between a polyphase system, AC/induction motors and AC electrical power generation.
ICE77 (talk) 03:33, 6 November 2016 (UTC)
thread_title:  Comments and inventors discrepancy 

message: "Common practice for rectifier installations and in HVDC converters is to provide six phases, with 60 degree phase spacing, to reduce harmonic generation in the AC supply system and to provide smoother direct current."
B.S.  The source is 3-phase, split into delta and wye components to provide unidirectional 6-pulse output of the rectifier. Sbalfour (talk) 23:06, 2 November 2017 (UTC)
replies: text: As far as I can tell, when counting phases of AC systems, you don't count a 180 degree (other half of a transformer) phase, but you do when counting phases for a rectifier. A three phase input, into a full wave rectifier, is a six phase rectifier system. Gah4 (talk) 23:40, 2 November 2017 (UTC)
thread_title:  Higher phase order 

message: From the article "Compared to a single-phase, two-wire system, a three-phase three-wire system transmits three times as much power for the same conductor size and voltage." 
Isn't the formula P=I*U*root(3) which makes it 1.73 times the power, not three times ? 
176.11.34.234 (talk)  —Preceding undated comment added 16:55, 8 June 2019 (UTC)
thread_title:  three phase power