Re (2): UPS with earth leakage device.
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From: ArameFarpado on 9 Jan 2010 06:19 Em Sábado 09 Janeiro 2010 05:28, jellybean stonerfish escreveu: > On Sat, 09 Jan 2010 00:05:57 +0000, ArameFarpado wrote: > >> Em Sexta 08 Janeiro 2010 18:28, jellybean stonerfish escreveu: >> >>> On Fri, 08 Jan 2010 13:17:38 +0000, ArameFarpado wrote: >>> >>>> anothter question if you don't mind: >>>> a lightning bolt falls in the ground at 6 meters from you and a cow, >>>> you suffer nothing while the cow gets electricuted and dies... why? >>> >>> Tennis shoes? >> >> bare feet just like the cow > > 2 legs?? the man has 2 legs and they are standing more or less at the same point, the cow has 2 legs about 1 meter apart from the other 2... ring any bells? > > On the side, just to keep this post entertaining... > > Q: Why did the cow say "Mooooove" ? don't know, no cow ever spoke to me... :)
From: Henrik Carlqvist on 9 Jan 2010 06:52 ArameFarpado <a-farpado.spam(a)netcabo.pt> wrote: > Em S�bado 09 Janeiro 2010 05:28, jellybean stonerfish escreveu: >> On Sat, 09 Jan 2010 00:05:57 +0000, ArameFarpado wrote: >>> Em Sexta 08 Janeiro 2010 18:28, jellybean stonerfish escreveu: >>>> On Fri, 08 Jan 2010 13:17:38 +0000, ArameFarpado wrote: >>>>> anothter question if you don't mind: >>>>> a lightning bolt falls in the ground at 6 meters from you and a cow, >>>>> you suffer nothing while the cow gets electricuted and dies... why? >>>> Tennis shoes? >>> bare feet just like the cow >> >> 2 legs?? > the man has 2 legs and they are standing more or less at the same point, the > cow has 2 legs about 1 meter apart from the other 2... ring any bells? <OT> If both the cow and the man were standing on their legs instead of lying flat on the ground or even better in some pit below the ground surface the lightning would not hit 6 meters from them. Instead the lightning would hit the highest point connected to the ground which would probably be the mans head. So my guess is that the cow has the best chance of surviving after all. </OT> regards Henrik -- The address in the header is only to prevent spam. My real address is: hc3(at)poolhem.se Examples of addresses which go to spammers: root(a)localhost postmaster(a)localhost
From: ArameFarpado on 9 Jan 2010 07:56 Em Sábado 09 Janeiro 2010 11:52, Henrik Carlqvist escreveu: > ArameFarpado <a-farpado.spam(a)netcabo.pt> wrote: > >> Em Sábado 09 Janeiro 2010 05:28, jellybean stonerfish escreveu: > >>> On Sat, 09 Jan 2010 00:05:57 +0000, ArameFarpado wrote: > >>>> Em Sexta 08 Janeiro 2010 18:28, jellybean stonerfish escreveu: > >>>>> On Fri, 08 Jan 2010 13:17:38 +0000, ArameFarpado wrote: >>>>>> anothter question if you don't mind: >>>>>> a lightning bolt falls in the ground at 6 meters from you and a cow, >>>>>> you suffer nothing while the cow gets electricuted and dies... why? > >>>>> Tennis shoes? > >>>> bare feet just like the cow >>> >>> 2 legs?? >> the man has 2 legs and they are standing more or less at the same point, >> the cow has 2 legs about 1 meter apart from the other 2... ring any >> bells? > > <OT> > > If both the cow and the man were standing on their legs instead of lying > flat on the ground or even better in some pit below the ground surface the > lightning would not hit 6 meters from them. Instead the lightning would > hit the highest point connected to the ground which would probably be the > mans head. So my guess is that the cow has the best chance of surviving > after all. > > </OT> > > regards Henrik you are driving away from the problem: the bolt didn't hit the human or the cow, it hit the ground or a tree at 6 meters from them, the man only gets scared while the cow dies electricuted... why? this is all related to the fact the earth's electrical potential is not the same in every place.
From: GangGreene on 9 Jan 2010 08:00 jellybean stonerfish wrote: > On Fri, 08 Jan 2010 20:12:39 -0500, GangGreene wrote: > >> ArameFarpado wrote: >> >>> Em Sexta 08 Janeiro 2010 19:41, Moe Trin escreveu: >>> >>>> On Fri, 08 Jan 2010, in the Usenet newsgroup comp.os.linux.hardware, >>>> in article <4b46e73e$0$280$14726298(a)news.sunsite.dk>, ArameFarpado >>>> wrote: >>>> >>>>>Joe Pfeiffer escreveu: >>>> >>>>>> ArameFarpado <a-farpado.spam(a)netcabo.pt> writes: >>>> >>>>>>> i can tell you that if you desconnect the earth, ther will be no >>>>>>> more a neutral in the output, you will have two live lines with a >>>>>>> voltage between them, and that could cause other issues. >>>> >>>> So by your definition, there can not be a "neutral" in a car or >>>> airplane. >>> no neutral, cars and planes have a body and one if it's poles is >>> connected to the body, usualy the negative pole. planes have a kind of >>> stick that touches he ground (and some cars also) to put the body at >>> the same potential as the ground they are standing; planes must have >>> this or people could get electricuted by touching the plane body after >>> a landing... some people more sensitive to estatic also place this >>> sticks in there cars so they don't get shocked when they touch them or >>> when the put the feet on the ground getting out of the car. >>> >>> >>>> And by the way, have you ever heard of an isolation transformer? >>> sure >>> >>>> Any idea _why_ they exist? >>> sure, it ain't got nothing to do with it is been discussed here. >>> >>> >>> >>>>>> Standard single-phase AC works with a hot line and a neutral line; >>>>>> neutral and ground are at the same potential. There should not be >>>>>> any current flowing through ground. >>>> >>>> As there is no current flowing in the ground wire, the voltage drop >>>> will be exactly the same at both ends of a ground wire. There is >>>> current flowing in the neutral (or 'return' lead, so the voltage will >>>> differ. Think about the consequences of that statement. >>>> >>>>>do you know how a neutral is created? >>>> >>>> It is a word - it means a common reference point. It's where you >>>> should place the black lead of your volt meter. >>> i didn't ask what it is or what it represents... how do you create one? >>> >>> >>> >>>>>just answer this >>>>> >>>>>a simple transformer from 230v to 110v, the primary receives a live >>>>>and a neutral, where is the neutral in the secundary side? >>>> >>>> Where was it defined. >>> there won't be one >>> >>> >>>> If all you have is two wires coming out of the transformer, you can if >>>> you desire define _EITHER_ OR _NONE_ as the reference point. >>> my point is, none of them will be a neutral >>> >>> >>>> That the two wires are now at some unknown potential with respect to >>>> earth only means the insulation is imperfect and there is some >>>> leakage. This is certainly a safety issue, >>> it is >>> >>>> but it doesn't >>>> prevent a motor, light, or computer attached to the secondary from >>>> working. >>> electronic sensible devices can be damage >> >> Guys/Gals Please >> >> One question.... >> >> How many wires from an electical substation to the trasformer on the >> pole? >> >> Answer One. >> >> There is no neutral. >> The power is returned through the earth, through a ground system. > > What power grid are you on? Don't know
From: GangGreene on 9 Jan 2010 08:22
ArameFarpado wrote: [putolin] >> >> Guys/Gals Please >> >> One question.... >> >> How many wires from an electical substation to the trasformer on the >> pole? > > 3 life phases, each AC with it's sinosoidal wave lagged 120º to the > others. every time 2 phases are positive there is one negative and > vice-versa. > > no need for neutral here. > >> >> Answer One. >> >> There is no neutral. >> The power is returned through the earth, through a ground system. > no. the electric circuit is closed between those 3 phases > > there is a triphasic wave form here > http://www.animations.physics.unsw.edu.au/jw/images/power_files/3phase.gif > > notice when 2 phases are positive there 1 negative and so on. > there is allways tension between them. > > http://www.windstuffnow.com/main/3_phase_basics.htm You are mixed up. I am talking residential power distribution you are talking appliance distribution. Notice only one leg of the 3 phase is coming down from the overhead 3 phase lines over head to the xmfr on the pole. If it was as you believe then two legs of the 3 phase would be in use. It's not. So tell me why is one leg used on the xfmr and one bare copper line going from the xfmr down the pole to a ground rod beside the power pole for then? Also when talking polyphase power distribution why then is a grounded conductor used/required on the service entrance drop from the pole to the residence? If it worked as you say it would only require two conductors to be brought to the residence. http://science.howstuffworks.com/power.html http://www.howstuffworks.com/framed.htm?parent=power.htm&url=http://www.epanorama.net/documents/groundloop/mains_connectors.html |