# Three Phase Electricity... **URL:** \ **Category:** Factual Questions\ **Created:** [March 21, 2003, 4:57am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026 "2003-03-21T04:57:38Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [March 21, 2003, 4:57am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/1 "2003-03-21T04:57:38Z")
Do power plants have three generators each 120 dgr out of phase to deliver three-phase electricity? This is just a WAG as a starting point, but I’m really just tossing darts blindly at the dartboard here! How is this done? I assume it is three phase from the factory, or is there a way to “create” three-phase downstream, as needed? I never quite understood this… - Jinx ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 21, 2003, 5:11am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/2 "2003-03-21T05:11:38Z")
One generator (strictly, alternator), three windings. The windings are spaced 120[sup]o[/sup] apart. You could also do it with 6, 9, 12… windings. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 5:11am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/3 "2003-03-21T05:11:41Z")
No, each armature of three armatures of the generator has windings arranged 120 degrees apart from each other. BTW, there are other polyphase systems in use, sucH as four-phase and nine-phase. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 5:13am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/4 "2003-03-21T05:13:12Z")
Of course I meant to say “each of three armatures”, etc. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [March 21, 2003, 5:14am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/5 "2003-03-21T05:14:15Z")
Sort of right. Each phase is created within wiring in the generator. Three phase power is produced by tripling the wiring. An explanation is [here](http://cipco.apogee.net/foe/fbagsp.asp) and [here](http://www.wikipedia.org/wiki/Three_phase) in more detail. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [March 21, 2003, 5:15am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/6 "2003-03-21T05:15:45Z")
Referring to the OP there, not the replies that snuck in. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 5:19am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/7 "2003-03-21T05:19:25Z")
Also, FWIW, there are two distint types of three-phase loads used. One is called a “delta” and is essentially three balanced loads arranged in a triangle shape with three linesa feeding the vertices, and the other is a “Y” with three unbalanced loads arranged in a Y shape, with a fourth neutral line at the apex of the the three feedpoints. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [March 21, 2003, 5:20am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/8 "2003-03-21T05:20:38Z")
Thanks, everyone! Truly Shocking! 😃 (Hey, I couldn’t resist!) ---
**Author:** ![hammerbach](https://avatars.discourse-cdn.com/v4/letter/h/73ab20/32.png) [@hammerbach](https://boards.straightdope.com/u/hammerbach)\ **Post date:** [March 21, 2003, 5:32am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/9 "2003-03-21T05:32:47Z")
The alternator in your car is likely three phase… ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 5:36am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/10 "2003-03-21T05:36:59Z")
AFAIKJ, automotive alternators are single phase. The number of phases depends not only upon the number of armatures, but the winding configuration of the armatures as well. ---
**Author:** ![Thaumaturge](https://avatars.discourse-cdn.com/v4/letter/t/858c86/32.png) [@Thaumaturge](https://boards.straightdope.com/u/Thaumaturge)\ **Post date:** [March 21, 2003, 5:45am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/11 "2003-03-21T05:45:15Z")
Airplanes use 400hz 3 phase power. ---
**Author:** ![hammerbach](https://avatars.discourse-cdn.com/v4/letter/h/73ab20/32.png) [@hammerbach](https://boards.straightdope.com/u/hammerbach)\ **Post date:** [March 21, 2003, 5:45am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/12 "2003-03-21T05:45:48Z")
Check out _Alternator Secrets_ by T.J.Lindsay. They are multple phase (not necessarily three) and then rectified thru diodes into rippled DC and regulated at the required voltage. Pretty cool. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 21, 2003, 6:01am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/13 "2003-03-21T06:01:41Z")
**Q.E.D.** , please stop referring to multiple armatures. On most polyphase machines, the stator is the armature. It has multiple windings, but there’s only one stator. It’s possible to make one where the rotor is the armature, but again, only one rotor with multiple windings. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 6:09am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/14 "2003-03-21T06:09:31Z")
I was using the term "armature"in this sense: > [@](#): > > armature > > \Ar"ma\*ture, n. (Elec.) That part of a dynamo or electric generator or of an electric motor in which a current is induced by a relatively moving magnetic field. The armature usually consists of a series of coils or groups of insulated conductors surrounding a core of iron. From [this sense](http://dictionary.reference.com/search?q=armature). ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 6:10am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/15 "2003-03-21T06:10:32Z")
Grrr…i meant “this article”. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 21, 2003, 6:18am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/16 "2003-03-21T06:18:06Z")
Yes, and I’m suggesting that you are using the term incorrectly. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 6:22am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/17 "2003-03-21T06:22:26Z")
I’ve always thought of an “armature” as an arm of the rotor assembly. I see now that is incorrect. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 21, 2003, 6:35am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/18 "2003-03-21T06:35:47Z")
The armature is the bit that isn’t the field. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 21, 2003, 6:40am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/19 "2003-03-21T06:40:08Z")
Thank you. I’ve dealt plenty with magnetics and three-phase circuits in transformer testing, but almost never with alternators, so I’m unfamiliar with terms which apply to them. I appreciate the information, **Desmostylus**. ---
**Author:** ![octothorpe](https://avatars.discourse-cdn.com/v4/letter/o/b77776/32.png) [@octothorpe](https://boards.straightdope.com/u/octothorpe)\ **Post date:** [March 21, 2003, 7:33am UTC](https://boards.straightdope.com/t/three-phase-electricity/163026/20 "2003-03-21T07:33:41Z")
**Q.E.D.** I believe you’re confusing armature with pole. The armature (rightly as you noted in your link) consists of a series of coils. The number and configuration of the coils (poles) determine how many phases are produced (i.e. multiples of 3 would produce 3Ø power). The armature is stationary and the rotor turns inside of it at a rate to produce the proper frequency. The rotor also consists of a number of coils which are energized (excited) to produce a magnetic field. This is accomplished either with an ‘exciter’ as an integral part of the generator, or with an outside excitation transformer which requires an outside source of power. So, a generator consists of a single rotor turning inside a single armature. I’m sorry, i can’t find my copy of the **Standard Handbook for Electrical Engineers** so my explaination is not as concise as it should be. Perhaps **David Simmons** or **Crafter Man** will chime in with the proper language. Also, it would be more correct to say there are 2 distinct type of 3Ø systems; delta and wye. A 3Ø load (motor for instance) does not require a neutral in order to operate, just the 3 phases. The neutral in the system serves 2 (main) purposes: 1) provides a path to the source should a phase come in contact with a ground. This allows the protection relays or breakers to open the circuit to prevent further damage to equipment and to eliminate an unsafe condition. 2) stabilizes the system voltage by providing a reference to ground. Depending on load balance, a strictly delta system may not read equally between all phases. Additionally, a wye system allows for more options in transformer connections. Although i can’t say for sure, i don’t know of any ‘strictly’ 4Ø or 9Ø systems. If i understand your meaning, 4Ø is generally referred to as 2Ø - 4 wire. Special transformers known as ‘Scott connected’ which have a ‘teaser’ winding connection at a point about 86% along the length of the primary coil. A second transfomer with a connection point at the midpoint of the primary coil is also used. These transformers were originally developed by Charles F. Scott and were used to convert the 2Ø output of the Niagra Falls generators to 3Ø. # [Next page](https://boards.straightdope.com/t/three-phase-electricity/163026.md?page=2)