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Re: [Amps] Safety grounding - was Mains Isolation Transformer

To: "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Safety grounding - was Mains Isolation Transformer
From: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 03 Jul 2006 12:33:17 -0700
List-post: <mailto:amps@contesting.com>
On Mon, 3 Jul 2006 04:43:45 -0700, R L Measures wrote:

>As I see it, under a volt is not a bane, and requiring two conductors  
>in a 240v circuit that carry zero current is inane..

In the UK (and the rest of Europe), mains power is 240 volts, with one of the 
conductors being a neutral (what North America electrical codes call "the 
grounded conductor"). In other words, it is just like our power, except that 
the "hot" or "phase" conductor is 240 volts above "ground" rather than 120 
volts. 

In the US, a 240 volt circuit is "balanced" -- that is, there is no grounded 
conductor, and each side is 120 volts above "ground." US 240 volt outlets 
REQUIRE a green wire (protective ground, or equipment ground). 

Another way of looking at it is that residential power is generally derived 
from a center-tapped 120-0-120 volt secondary. In large buildings, it is 
generally derived from 120/208V 3-phase power. In Europe, it is derived from 
a center-tapped 240-0-240 secondary or 240/420 volt 3-phase. 

All of this is covered in considerable detail in the tutorial on power and 
grounding on my website. http://audiosystemsgroup.com/publish 

Jim Brown K9YC


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