"Dimitrios Tzortzakakis" schreef in bericht
...


--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Larkin" ?????? ???
?????? ...
On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
wrote:


At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."


Hmmm...

Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?

Very high AC currents are much more common.The output of a moderate 300 MW
alternator is 10 kA at 21 kV.A nuclear power station alternator with a
voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
MVA.Always talking about balanced three-phase systems.The output of the
300
MW power-station at 400 kV transmission voltage is just 400 A.Conductors
in
all LV circuits are made of electroletically purified solid copper, 99,99
%
Cu.In MV, HV and EHV distribution and transimission voltages respectively,
they use ACSR conductors (Aluminium Conductor Steel Reinforced)that have a
steel core, but an aluminium outer sheath.

Sometimes you have something like Aluminium inside (for the weight) and
Cupper on the outside for conductivity. Due to the Skin Effect this is where
the most (AC) current will flow.
On some application I have even seen Cu on the inside and Au on the outside,
my guess there is at least one other material between the two for obvious
reasons.

Alexander (ACE, Applied Communications Engineer)