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Date:      Thu, 17 Oct 2013 15:10:20 +0200
From:      Ralf Mardorf <ralf.mardorf@alice-dsl.net>
To:        freebsd-questions@freebsd.org
Subject:   OT: UPS buying suggestion
Message-ID:  <1382015420.5852.97.camel@archlinux>
In-Reply-To: <525FD4C8.1090600@fjl.co.uk>
References:  <CACo--msUpY-6r7MkuEvrPDpSVdFZyBotSA-eS7aLGMFDeq_vDQ@mail.gmail.com> <alpine.BSF.2.00.1310150911510.97788@wonkity.com> <CACo--mvUfcAy=0hyun21DZwSmdd=SmP7EeU-FVxJyiT_h4Rxkg@mail.gmail.com> <525F0138.1020304@fjl.co.uk> <20131017093820.6a8428de@X220.ovitrap.com> <alpine.BSF.2.00.1310162309200.14022@wonkity.com> <1381988697.5852.16.camel@archlinux> <20131017142910.61325830@X220.ovitrap.com> <1381992680.5852.45.camel@archlinux> <525FD4C8.1090600@fjl.co.uk>

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On Thu, 2013-10-17 at 13:15 +0100, Frank Leonhardt wrote:
> On 17/10/2013 07:51, Ralf Mardorf wrote:
> > On Thu, 2013-10-17 at 14:29 +0800, Erich Dollansky wrote:
> >> Industry is much worse. Their machines made early computers fail when
> >> the bigger machines started work.
> > I worked for an audio company. The audio workshops were rented rooms on
> > a farm, and the boss missed to check the values of the RCCB, which
> > nearly killed a friend. Bigger machines are a PITA ;). The RCCB had a
> > value that high, that it was dangerous to life for an audio workshop. A
> > big machine not only pollutes the mains, if you turn it on, it also will
> > "eat" the complete power and lots of it going in, doesn't come out. A
> > "normal" RCCB would turn off immediately.
> >
> >
> Most RCCB (aka ELCB, RCD) work (hereabouts anyway) work with 
> counter-wound coils on the input and output of the supply such that he 
> magnetic field is neutral if the current is the same. If it goes out of 
> balance, it trips the switch. Normally 30mA difference is the rule. They 
> don't have a value, as such. I heard that only 10mA is needed to 
> interrupt your heart, but I've also heard 100mA. They're all potentially 
> dangerous. It depends on the route taken by the current passes through 
> your body - you'd have to try quite hard to get even 10mA in the wrong 
> place, but I guess you could do it with rubber shoes and grasping the 
> mains one your one hand and an earth spike with the other. I was taught 
> to keep my left hand in my pocket when poking around stuff that might be 
> live, and do it quite subconsciously.

The one at home, in Germany called FI, has got a value of 0.03A for my
flat, the one at the farm had a value of 1A.

"Handelsüblich sind Fehlerstromschutz-Schutzschalter in der Bauart A für
Bemessungsdifferenzströme von IΔN=10 mA, 30 mA, 100 mA, 300 mA, 500 mA
und 1 A." -
https://de.wikipedia.org/wiki/Fehlerstromschutzschalter#Kennwerte

The keyword is "Bemessungsdifferenzströme", sorry I can't translate it.
30mA is save, 1A will kill you, since it won't turn off the power if
your body should become the resistor.

As mentioned before, a workshop in addition must use an isolating
transformer, by this galvanic isolation you can't get an electric shock
if you only have contact to the phase and ground. You need to have
contact to phase and neutral conductor to get a shock.




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