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List:       opensuse
Subject:    Re: [opensuse] KTp alternative to Skype?
From:       Greg Freemyer <greg.freemyer () gmail ! com>
Date:       2014-05-06 18:45:10
Message-ID: CAGpXXZKGyeJNan4BiUaEOE-JmhJ+tomN2TJ0SuZAiwt1qabQMw () mail ! gmail ! com
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On Tue, May 6, 2014 at 2:26 PM, Per Jessen <per@computer.org> wrote:
>> Using a 2-phase US circuit to simulate a 1-phase 220v circuit would be
>> dangerous if there are devices that depend on one of the legs being
>> ground.
>
> I suspect you mean neutral instead of ground?

At least here neutral and ground are very similar.

A standard US household circuit breaker panel has:

phase 1 hot
phase 2 hot
neutral - return
ground

The neutral & ground are actually tied together inside the circuit
breaker panel.  Further, both are often connected to a copper cold
water line.  By code that has to happen close to where the cold water
line enters the building.  I know my house works that way, but there
is also a second ground spike driven directly into the ground that is
also tied to the circuit breaker panel ground and neutral.

Thus in theory the "ground"/neutral is actually a part of the 120volt
circuit. and both the ground lines and the neutral/return should have
close to zero volts differential to the outside dirt (ground).

The fundamental difference here is that the ground lines running to
every plug don't typically carry any current except in a failure mode.
 The neutral/return is meant to carry current routinely.

With a "class II" plug, the active legs slots are slightly different
sized so that a device can know which leg is neutral (close to ground)
and which leg is hot.

http://upload.wikimedia.org/wikipedia/commons/d/dd/OutletPlug.jpg

fyi: if a circuit breaker panel is perfectly balanced the electrons
flow only in the 2 hot lines and in the neutral.  No electron movement
would take place in any of the ground lines including the real ground
outside.  Such perfect balancing is impossible to achieve so electrons
are moving in and out of the earth continuously in a US system.  I
assume the same is true for the EU.

Greg

--
Greg Freemyer
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