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Old 25th May 2012, 12:13 PM   #12371
labjr is offline labjr  United States
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I've had a debate with a friend about the difference between US and European power. He thinks there is something different about the phase and says a 220v motor will not work on both systems. To me, the power is basically the same except for a center tap which is used as the neutral in the US.

Last edited by labjr; 25th May 2012 at 12:15 PM.
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Old 25th May 2012, 12:33 PM   #12372
AndrewT is offline AndrewT  Scotland
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The 50Hz or 60Hz difference could be the compatibility problem.
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Old 25th May 2012, 01:26 PM   #12373
Floric is offline Floric  Europe
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Quote:
Originally Posted by Paulv View Post
hello Floric
what a long explanation! I learned something:
the difference with here in france is that you connect neutral to earth BEFORE the meter, circuit breaker etc, which in a way is a good thing (lower resistance of the earth), and from there you split again phase, neutral (those are going through the circuit breaker) plus ground wire that runs direct.
Even if you are sure which is the neutral you should never connect it to the case, in the event of a fault (live wire touching the case) the circuit breaker would not trip.
You are right, the circuit breaker would trip only if someone touches the case. If it is sensible enough (30mA e.g.), this is not very pleasant but far from lethal. In most cases the fuse will blow because of the short circuit.

Quote:
back to hifi:
many systems have only two wire connection: neutral and live
the common ground between appliances (CD preamp, amp, tv) is done through signal (audio) cables and the whole system is left "floating" , no reference to earth, which is OK with good transformers and isolation, if you had two ground connections in each appliance (the socket ground plus the signal ground) you would have ground loops which generate hum.
It can be usefull to have your system referenced to ground but then connect only one appliance to your socket ground (NOT THE NEUTRAL), and do it on the small signal appliance (cd, turntable).
... balanced connection have a high immunity to ground loops, noise and hum...

lastly: are we off topic????
cheers
Paul
Hello Paul,

to get even more back to the topic. Look into http://www.firstwatt.com/pdf/prod_f5_man.pdf page 18. The gorund of the PS is connected to ground via a thermistor (which acts as a ground loop breaker to avoid hum and could be left out). You may find hundreds of examples construced like that sometimes with ground loop breaker or ground loop resistance, sometimes without.

I think an F5 would not work correctly without even if other devices do because they are constructed different. There might be cases where a setup like this will work, but not in every case.

But with this construction you "earn" an additional risk: In the case of a fault in the transformer you may get line voltage at the case (which is connected to ground too).

To find a solution to the F5 problem above: Whi not connect the case of the computer so the case of the F5?

Regards

Flo
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Old 25th May 2012, 01:52 PM   #12374
nar is offline nar
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Quote:
Originally Posted by Floric View Post


To find a solution to the F5 problem above: Whi not connect the case of the computer so the case of the F5?

Regards

Flo
I would star Earth directly to each of any metallic enclosures, not "chainwire" it for safety reasons. In F5 leave the audio ground float from chassis with only a CL60 from audio star ground to chassis. Hope this helps,

Best,

nAr
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Old 25th May 2012, 02:04 PM   #12375
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Originally Posted by AndrewT View Post
Surely this can't be true.

In Europe (we have the harmonised power supply) the mains power is fed in via the Live and returns via the Neutral.
over here youcan turn the plug 180 degree and plug it back in. so no live/netrual.
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Old 25th May 2012, 02:11 PM   #12376
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here is the typical plug
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Old 25th May 2012, 02:26 PM   #12377
labjr is offline labjr  United States
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In USA we can turn around the plug too on some lamps etc. Some appliances have polarized plugs. In either case neither the neutral nor hot wire is connected to chassis. The neutral conductor is at the same potential as earth ground. I imagine it's the same for you.
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Old 25th May 2012, 02:56 PM   #12378
nar is offline nar
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Originally Posted by AudioSan View Post
over here youcan turn the plug 180 degree and plug it back in. so no live/netrual.
It doesn't mean you don't have live/neutral. We can do it too here in France and there is indeed live / neutral. Mains is asymetric by nature, i.e. one can measure 230V between Live and Neutral, but also Live and Earth. But between Neutral and Earth you don't have anything significant in general.

Do bear in mind that the power is distributed in 3 phases (triphase) before big district xformer. Once here all loads (phases) are power-balanced against it, and Neutral is a special return path to the big xfo they assign you. So between phases you would have 380V, perhaps your neighbour has a different phase from xfo than you but perhaps the same. Between Phase and Neutral they give you you have the 230V ...

Best,

nAr
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Old 25th May 2012, 03:21 PM   #12379
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i would suggest getting one of the neon bulb pocket line-testers. once you've wired up the amp make sure that the switched side is the "hot".

there's a "differential scope probe" video with folks from Nat Semi (Bob Pease RIP among them) and a Tektronix sales/tech rep on youtube -- one of the guys said to the Tek technical rep "the first thing i do when i get a new scope is cut off the ground plug". Can't see it on the video, but i am sure that the Tektronix guy's eyes were rolling around in the back of his head.

and 30mA is more than enough to kill ya.
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Old 25th May 2012, 04:38 PM   #12380
Floric is offline Floric  Europe
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Quote:
and 30mA is more than enough to kill ya.
That's right but the lethality (right word?) depends on the time the current flows through the body. Normal differential circuit breakers, at least the ones used in households, have switching times from 20ms to 40ms. The 30mA can kill you if they flow for more than 1s. For 20ms you would survive 500mA.

But I would not try it, better to avoid accidents like that.
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