Yes, you are probably right,  I will look for a local professional guy to
come and get things going.  At least I have an idea of what is
happening...

Thanks for the advice

On Fri, Nov 11, 2011 at 10:54 AM, gene heskett <ghesk...@wdtv.com> wrote:

> On Friday, November 11, 2011 11:28:02 AM Peter Blodow did opine:
>
> > 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've been following this thread, debating if I should jump in, but now that
> Peter has said it, I concur heartily with his advice.
>
> Its easy enough to be crispy critter'd around mains power, I've damned near
> done it to myself at least 3 times in my work around tv stations where we
> may be the local power companies largest customer. 2nd degree burns on both
> arms & the at the instant bare chest, will take ALL the starch out of you
> for a few days, and likely lay you up with the shingles for a month or
> more.  Been there, done that, it will totally redefine your personal pain
> threshold, upwards.  No one needs that but somehow I kicked loose and
> survived.
>
> Simply put Brian, if you need to ask these questions, then get a licensed
> pro who is intimately familiar with the local codes and let him do it.  We
> aren't there and in some cases in this thread are trying to be helpful with
> inadequate information and almost zero knowledge of local codes.
>
> Old buildings with grandfathered in electrical supplies can be legal, and
> lethal.
>
> > 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 <e...@dc9.tzo.com> 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<bmihu...@hulkster.net>
> 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
> > >>>>> ------------------------------------------------------------------
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> > >>>>
> > >>>> 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
> > >>>>
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> > >>
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>
> Cheers, Gene
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> My web page: <http://coyoteden.dyndns-free.com:85/gene>
> They call them "squares" because it's the most complicated shape they can
> deal with.
>
>
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>



-- 
Brian May
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