Re (2): UPS with earth leakage device.
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From: Joe Pfeiffer on 8 Jan 2010 15:05 ibuprofin(a)painkiller.example.tld.invalid (Moe Trin) writes: > 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. And by the way, have you ever heard of an isolation > transformer? Any idea _why_ they exist? > >>> 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. Differ, yes. If the neutral wire is properly sized, it will not differ significantly. -- As we enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously. (Benjamin Franklin)
From: ArameFarpado on 8 Jan 2010 19:05 Em Sexta 08 Janeiro 2010 17:08, Joe Pfeiffer escreveu: > ArameFarpado <a-farpado.spam(a)netcabo.pt> writes: > >> Em Sexta 08 Janeiro 2010 12:40, Joe Pfeiffer escreveu: >> >>> ArameFarpado <a-farpado.spam(a)netcabo.pt> writes: >>> >>>> Em Sexta 08 Janeiro 2010 01:40, Joe Pfeiffer escreveu: >>>> >>>>> ArameFarpado <a-farpado.spam(a)netcabo.pt> writes: >>>>> >>>>>> Em Quinta 07 Janeiro 2010 08:27, no.top.post(a)gmail.com escreveu: >>>>>> >>>>>>> No, AFAIK the earth-leakage -detector works by measuring >>>>>>> the unbalance between the line and neutral current flow. >>>>>>> Since the unbalance must be returning via the earth. >>>>>>> So REMOVING THE EARTH to the UPS & computer circuit >>>>>>> 'eliminates the problem'. But that's a bodge. >>>>>>> One needs to fully understand the problem cause >>>>>>> sequence. >>>>>>> . >>>>>>> == TIA. >>>>>> >>>>>> if you have electrical questions, it's better to put them in >>>>>> sci.electronics.basics >>>>>> >>>>>> >>>>>> 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. >>>>> >>>>> You can tell us anything you want, but if you tell us that you're >>>>> wrong. 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. >>>> >>>> do you know how a neutral is created? >>> >>> The most relevant part of the answer is probably that it's bonded to >>> ground at the service panel. >> >> correct, it's connected to earth but not by the same connection you have >> in you house... >> >> every house has its own earth connection, the neutral is created by a >> earth connection in the last transformer of the company that distributes >> the energy. this is why the neutral may or may not have the same >> electrical potential as the house's earth. the same way two houses's >> earth wiring may not have the same potential. > > I guess I wasn't explicit enough: it's bonded to ground at *your* > *house's* service panel -- i.e. the "breaker box". The whole point is > to avoid having neutral at a different potential than ground. No it isn't, not in europe anyway... neutral comes from the outside allready a neutral, it's discharge is done right in the secundary side of the transformer that feeds the bilding or block of bildings. and that is done with several copper rods sticked in the ground then every bilding has it's own copper rod, and it's earth does not connect with neutral... it's commom to have about 2volts between earth and neutral over here. > >> 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? you don't know why? >> >> >>> >>>> 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? >>> >>> And the relevance of this to mains wiring is... >> the output of a ups is not connected to the mains wiring. >> if the op desconnect the earth wire, he will loose the neutral on the >> output, if this ups is feeding several machines that could be a problem > > Ah, OK -- not necessarily. Depends on the UPS configuration. Either > the neutral is passed through (if it doesn't meet the NEC requirements > for a "separably derived source"), or it is grounded within the UPS (if > it does). neutral can't pass trought, an ups is not a light switch > I'm not familiar with the internal details of typical home PC > UPSs, and familiar enough with the relevant parts of the code but I'd be > pretty surprised if a plug-in UPS were permitted to be a separably > derived source. well, i've been talking about real ups... the ones that stay hidden and feed a hole network of computers, i have one in the company i work that feeds about 400 pc's, including monitors, printers and so on... that thing is about 2 meters tall, 1 meter sideways, and we have to replace it's batteries every 3 years. most home ups aren't really ups at all, some of them can't even feed the pc after the main power is gone, they are isolation transformers.
From: ArameFarpado on 8 Jan 2010 19:05 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
From: ArameFarpado on 8 Jan 2010 19:12 Em Sexta 08 Janeiro 2010 13:42, Joe escreveu: > On 2010-01-08, ArameFarpado <a-farpado.spam(a)netcabo.pt> wrote: >> Em Sexta 08 Janeiro 2010 12:40, Joe Pfeiffer escreveu: >> >>> ArameFarpado <a-farpado.spam(a)netcabo.pt> writes: >>> >>>> Em Sexta 08 Janeiro 2010 01:40, Joe Pfeiffer escreveu: >>>> >>>>> ArameFarpado <a-farpado.spam(a)netcabo.pt> writes: >>>>> >>>>>> Em Quinta 07 Janeiro 2010 08:27, no.top.post(a)gmail.com escreveu: >>>>>> >>>>>>> No, AFAIK the earth-leakage -detector works by measuring >>>>>>> the unbalance between the line and neutral current flow. >>>>>>> Since the unbalance must be returning via the earth. >>>>>>> So REMOVING THE EARTH to the UPS & computer circuit >>>>>>> 'eliminates the problem'. But that's a bodge. >>>>>>> One needs to fully understand the problem cause >>>>>>> sequence. >>>>>>> . >>>>>>> == TIA. >>>>>> >>>>>> if you have electrical questions, it's better to put them in >>>>>> sci.electronics.basics >>>>>> >>>>>> >>>>>> 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. >>>>> >>>>> You can tell us anything you want, but if you tell us that you're >>>>> wrong. 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. >>>> >>>> do you know how a neutral is created? >>> >>> The most relevant part of the answer is probably that it's bonded to >>> ground at the service panel. >> >> correct, it's connected to earth but not by the same connection you have >> in you house... > > Actually, it is. not in europe >> >> every house has its own earth connection, the neutral is created by a >> earth connection in the last transformer of the company that distributes >> the energy. this is why the neutral may or may not have the same >> electrical potential as the house's earth. the same way two houses's >> earth wiring may not have the same potential. > > They do. Reason? you stick 2 copper rods in the ground separated by 50 meters and you can have potential between them diferent bildings don't share earth connections, that could be dangerous. > Standard home wiring these days includes tying > neutral to ground. not in europe > At any outlet in your house, if properly wired, > neutral and ground are the same. no
From: ArameFarpado on 8 Jan 2010 19:25
Em Sexta 08 Janeiro 2010 19:42, Moe Trin escreveu: > On 08 Jan 2010, in the Usenet newsgroup comp.os.linux.hardware, in article > <slrnhkedim.jbd.joe(a)barada.griffincs.local>, Joe wrote: > >>ArameFarpado <a-farpado.spam(a)netcabo.pt> wrote: > >>> every house has its own earth connection, the neutral is created >>> by a earth connection in the last transformer of the company that >>> distributes the energy. > > This statement is false. The "neutral" is created by people following > a standard and DEFINING "this" wire with respect of one or more "hot" > leads. ??? > > Go out and buy two or three eight foot (2.44 meter) long copper-clad > ground rods and take them into the yard of your house (or a nearby > park - I don't care). Drive each ground rod vertically into the > ground such that the top of the rod is flush with the surface and at > least ten feet (3.05 meter) away from each other. Now take an Ohm > meter and measure the resistance between each rod. It won't be zero. > So, which one of the ground rods is at the true ground? each one of them is a true ground related to the place they wore stick you people got to understand one thing: talking about the planet's ground it isn't all at the same electrical potential in every place. electricity is a part of nature, it's everyware and it is in a constant movement, diferent places can be at diferent electrical potentials. in teory; you can get electricuted by standing with your feet on the ground an touch a earth wire whose rod is placed at 10Km from you. |