Ek's Home   |   Forum   |   Chat   |   Electrical Links   |
	Subject - Single Phase? veganfan From the way I understand three phase electricity. The other two legs carry the extra current from the leg that is at its highest point back to source. This is why you do not always need neutral wire. For example phase A at 277v then phase b at-138.5 and phase C at -138.5 so add them up it is 0v. Because when phase A at 90degrees then B at 210 and C 330 since they fallow sine wave sine 90 is 1 sine 210 is -.5 sine 330 is -.5 Well any way how does single phase work off 480 y style? First of all is it really single phase? I mean it has phase A & B for example. Plus we never pull a neutral, but no current on ground? So if leg A at 277v and B at – 138.5v then current fallowing voltage. Then leg B should not handle current leg A is supplying. So any why how can this work mathematically not possible. I am I missing something? Please help frenchelectrician ahh welcome to the fourm here veganfan; what you are describint a true single phase circuit but get in three phase system it is little diffrent and tricky here . i will try my best to explain to you here ok now . for 277/480 volt wye system : line to line is 480 volts reguard what hot leg you pick from but for line to netral is 277 volts. and the real three phase rotation is 120 electrial degrees apart not like single phase system is 180 degress apart . you can see why the voltage is diffrent for single and three phase are not the same. let me make a sample here imaged the transformer here for single phase transformer with mid tapped netural each hot leg is 240 volts but from the hot leg to netural is 120 volts. the three phase system somehow run diffrent here imaged 3 single phase transfomers here and conneted diffrent here have 3 hot legs here and common netural ( both 120/208 volts and 277/480 volts are same way but diffrent voltage level ) take each hot leg to other hot leg will be like 480 volts but get one hot leg to netural is 277 volts because of square roots of 3 mean 1.73 of true 3 here. right now i cant find a photo how the three phase do run like this. but someone will come up a idea with it merci, marc iwire First when you say "This is why you do not always need neutral wire" how do you mean that, 277 lighting or a 3 phase motor? Second three phase is never 90 degrees, each phase is 120 degrees apart. There never is a time when two phases are opposite, that is why when you use only 2 phase conductors and a neutral to make a Multiwire branch circuit the neutral is a current carrying conductor, use all 3 phase with a neutral and the neutral only carries the imbalance of the hots. What is it that you never pull a neutral to? frenchelectrician here i will try to put a link here to see if this graphic work here http://home.comcast.net/~ronaldrc/wsb/html/view.cgi-image.html--SiteID-1344378.html and the second one here too. http://cast.csufresno.edu/agedweb/agmech/graphics/Electricity5a.gif merci , marc p.s. if feel need to keep in the some kind of photo file you can move it there if need to. JimmyDee Some great graphics. Thanks. Jim veganfan .Thanks for help. If reread my post you will realize that I used 120 degrees to separate each leg this much I understand. I have been through transformer theory and do realize difference in single phase as in 120/240 vs. 480/208 ect. But with this being said when you take two out of three legs like we do at work with no transformer it does not make since. 277 for lighting does because you use one leg and a neutral not two legs with out neutral. veganfan Using the link that was posted. You can see what I mean as red leg is high, blue and black are at at exactly -.5 off red there for adding to zero, but if you take blue leg away then not so. Also at my work we never pull a neutral in for motors. Only lights. karlwayne I'm guessing but I think you're looking at this from the wrong angle. Let's say you took 480V single phase from your 277/480 panel to feed a single lite pole. No matter which two legs you use, at any given instant of time, you will always have 480V between them. Your total current in both legs is also always the same (per any given instant of time) If you want to add these numbers, which are out of phase 120 degrees, you would have to do it vectorially. Scott Vickrey Marc do any of these illustrations belong to you? C'est la seule manière que nous pouvons les employer dans le remerciement vous de l'offre Je crois que le monde devrait parler français que c'est une langue retentissante de satisfaction. C'est pourquoi il ne partira jamais. Le marc I a employé Google comment il s'est avéré? Malheureusement, je ne puis pas parler français. Je puis parler italien. J'ai habité dans Sicilia pendant deux années. Le marc si vous me présentez à une fille française et me commanditez je viendra visite vous. frenchelectrician Bonsoir scott , le lien que j'ai fourni dans le fourm. j'ai fait une petite erreur là que je devrais prouver la source d'emplacement d'où elle est venue et je corrigerai mon erreur ici, svp accepte mes excuses pour mon erreur ici et si vous me voulez au corret il me fais savoir. beaucoup de mercis de votre temps. merci, marc i will translated in engish in here too in case some of the members get confused what i am saying in here and i will provide the link for french translator too if ok with you. the link that I provided in the fourm. I made a small error there which I should prove the source of site from where it came and I will correct my error here, please accept my excuses for my error here. and if you want me with the corret it let me know thanks for your time. merci[thanks] , marc this link is from translator www.trans.voila.fr/voila scott, i was born and raised in Metro de Paris France and i am fluent in french , engish and signlangune for the deaf . if any question you are welcome to ask me iwire Marc, I have been to France, can not speak French though. I stayed in a small town not far from Paris, Espaly I think it was. I was just 13 then and went to visit some French friends of my parents, they took us to the Moulon Rouge, that was an eye opener for me then. I do remember the subways and trains where great, nothing like ours. Bob