On Fri, Nov 11, 2011 at 10:01 AM, Peter Blodow <[email protected]> wrote:
> Brian, > looking at your questions I get the feeling that you are a bloody > beginner as far as power electricity is concerned. I get the scares > imagining what you could possibly do to yourself and others, > experimenting with your mains supply. It would be much safer for you and > would calm my nerves (and apoparently other's, too) if you'd call a > local electrician to wire the basic supply of your machinery or what you > have. It's worth your life's value. Please get yourself some sound > advice! This is not electronics where a fault only results in a burned > up transistor or so. > > I am asking questions to get sound advice. Yes I am a beginner at power electronics. That is why I am asking the question. I am reading what I can and asking different people before I do anything. I am in no hurry and not planning to wire anything until I understand what I am doing. Currently I just have the 3 phase power to the VFD and the rest from an extension cord in the wall. It works, but I would like to improve the design. I have to learn somehow and will probably ask beginner questions.... So far people have given me further links to read and different things to search on google to understand better. > To make it clear: grounding is the up and down of electrical power > application. Imagine only a little high resistance insulation fault in > the primary of your local high voltage transfomer - if the secondary > would not be grounded in some way, in this case you could easily > experience 10 or 20 kV on your home outlet.... In case the secondary is > ground referenced by connecting the center tap of the secondary windings > to ground, this fault might not even be noticed! Floating potentials are > a highly dangerous thing, never leave any circuit unreferenced to ground! > > Peter Blodow > > > > > > Brian May schrieb: > > Sent from my iPod > > > > On Nov 10, 2011, at 10:30 PM, Dave <[email protected]> wrote: > > > > > >> Usually bigger 3 phase machines being fed with 480 volts or so will only > >> have the 3 phases run to the machine without a neutral wire. > >> > >> The reason being that Line to Neutral on a 480 volt system is 277 volts > >> and that is not very useful for anything other than lighting. > >> > >> To get 120 VAC, two of the phases will be tapped (480 volts) and that > >> will be run to a step down transformer. > >> One the secondary side of the transformer, one leg of the transformer > >> will be declared the hot line, and the other leg will be declared the > >> neutral. > >> The neutral will be bonded to the ground close to the transformer. > >> The hot line is fused. That will establish a proper 120 VAC circuit > >> off the 3 phase input power. > >> > > > > What is meant by "bonded to the ground"? Does that mean connecting the > nuetral leg of the transformer to the ground? If so, why use the > transformer at all when i can just go from a leg to ground? > > > > > > > >> You could run a separate single phase feed into the existing 3 phase > >> power panel, but then you would have power being fed into one panel from > >> two different sources and that gets tricky from a safety standpoint. > >> I try and avoid doing that whenever possible. > >> Generally when you pull the disconnect switch on a machine panel you > >> want to kill all power in the panel for safety. > >> > >> A lot of machine builders are now avoiding 120 volt power system in > >> their machines entirely. They do that by using DC power supplies that > >> can accept high voltage input power directly. > >> > >> You can buy 3 phase input power supplies that will accept up to 600 VAC > >> and produce 24 VDC. Most of the big power supply makers sell them. > >> > >> Dave > >> > >> > >> > >> On 11/10/2011 10:27 PM, Brian May wrote: > >> > >>> Ok that makes sense. > >>> > >>> Just out of curiosity, How do other machines do it. Our other cnc > machines only have the 3 lines and earth ground running into them... > >>> > >>> Sent from my iPod > >>> > >>> On Nov 10, 2011, at 9:01 PM, Brian Mihulka<[email protected]> > wrote: > >>> > >>> > >>> > >>>> On 11/10/2011 08:50 PM, Brian May wrote: > >>>> > >>>> > >>>>> This is probably an easy question for alot af the people on the list. > >>>>> > >>>>> I have 3 phase power going to my vfd on my machine. I want to the > use that same power to power all the 120 single phase components. (the dc > power supply for the steppers and varios other motors. ). This way i only > need 1 plug > >>>>> > >>>>> I have been reading and people say i can go from 1 leg to a nuetral > or leg to leg. I do not have a nuetral line so my question is will it be ok > to go from leg to leg for the 120 single phase? Or is there some other > component i need? > >>>>> > >>>>> Thanks > >>>>> Brian > >>>>> > >>>>> Sent from my iPod > >>>>> > ------------------------------------------------------------------------------ > >>>>> RSA(R) Conference 2012 > >>>>> Save $700 by Nov 18 > >>>>> Register now > >>>>> http://p.sf.net/sfu/rsa-sfdev2dev1 > >>>>> _______________________________________________ > >>>>> Emc-users mailing list > >>>>> [email protected] > >>>>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>>>> > >>>>> > >>>> If its 3 phase 208, one leg to any other leg will give you 208. You > >>>> have to have the neutral to get 120 from any leg. You should get 120 > >>>> from any leg to ground but it wouldn't be up to code. > >>>> > >>>> Brian > >>>> > >>>> > ------------------------------------------------------------------------------ > >>>> RSA(R) Conference 2012 > >>>> Save $700 by Nov 18 > >>>> Register now > >>>> http://p.sf.net/sfu/rsa-sfdev2dev1 > >>>> _______________________________________________ > >>>> Emc-users mailing list > >>>> [email protected] > >>>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>>> > >>>> > >>> > ------------------------------------------------------------------------------ > >>> RSA(R) Conference 2012 > >>> Save $700 by Nov 18 > >>> Register now > >>> http://p.sf.net/sfu/rsa-sfdev2dev1 > >>> _______________________________________________ > >>> Emc-users mailing list > >>> [email protected] > >>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>> > >>> > >>> > >> > ------------------------------------------------------------------------------ > >> RSA(R) Conference 2012 > >> Save $700 by Nov 18 > >> Register now > >> http://p.sf.net/sfu/rsa-sfdev2dev1 > >> _______________________________________________ > >> Emc-users mailing list > >> [email protected] > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > > > > > ------------------------------------------------------------------------------ > > RSA(R) Conference 2012 > > Save $700 by Nov 18 > > Register now > > http://p.sf.net/sfu/rsa-sfdev2dev1 > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > ------------------------------------------------------------------------------ > RSA(R) Conference 2012 > Save $700 by Nov 18 > Register now > http://p.sf.net/sfu/rsa-sfdev2dev1 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Brian May 506.8862.9162 (Cell) 506.2293.6375 (Office) ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
