Re (2): UPS with earth leakage device.
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From: Joe on 8 Jan 2010 08:42 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. > > 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? Standard home wiring these days includes tying neutral to ground. At any outlet in your house, if properly wired, neutral and ground are the same. -- Joe - Linux User #449481/Ubuntu User #19733 joe at hits - buffalo dot com "Hate is baggage, life is too short to go around pissed off all the time..." - Danny, American History X
From: Joe Pfeiffer on 8 Jan 2010 12:08 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. > 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? > > >> >>> 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). 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. >> >>>> >>>> See http://en.wikipedia.org/wiki/Ground_and_neutral >>> i don't have to see anything, you have, and stop reading that fake >>> encyclopedia >> >> The fake encyclopedia bases its answer on the National Electrical Code. > not really, i myself wrote part of a article in wikipedia... > anyone qcan wrote articles in there. > >> Show me a source you regard as more authoritative that disagrees. > learn electricity... That's not a cite I'll recognize, sorry. -- 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: jellybean stonerfish on 8 Jan 2010 13:28 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?
From: Moe Trin on 8 Jan 2010 14:41 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. >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. >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. 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. 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, but it doesn't prevent a motor, light, or computer attached to the secondary from working. If you do connect one of those leads to ground, you will reduce the risk to a person touching _that_ lead while grounded, and increase the risk if the person touches the _other_ lead. >i don't have to see anything, you have, and stop reading that fake >encyclopedia You know you're right, and don't want facts to get in the way of that belief. Free clue - look at the _references_ that the ``fake'' encyclopedia cites. Old guy
From: Moe Trin on 8 Jan 2010 14:42
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. >> 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? Standard home wiring these days includes tying >neutral to ground. Within the distribution panel, the neutral and ground will be at the same relative potential. If you compare the voltage between that point in one house with the same point in another house, there will be a difference - very small, but it will exist and be measurable. The reason: wires and ground have finite resistance, and any current flowing through those wires creates a voltage difference according to Ohms Law. 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? >At any outlet in your house, if properly wired, neutral and ground >are the same. WRONG! What is the resistance of #14 AWG hard drawn copper wire? #10AWG? What is the relationship between voltage, current and resistance? As there is no current flowing in the ground wire, what is the voltage drop across fifty feet of #14? What's the voltage drop with twelve amperes? I don't think it's zero, and before you whine that the results are so low that they wouldn't hurt anyone (about 1.57 volts), try operating an audio or video system with that much difference in neutral voltage between components like a receiver and recording device. Old guy |