The Skin effect is an electrical phenomenon that forces the current towards
the surface of a conductor when the frequency rises. The smaller area the
current use makes the total resistance higher. The effect can be explained
as the conductor's inductance close to the centre is higher than further
out because it is surrounded by a higher magnetic flux and a back-e.m.f.
is induced. This also makes the phase of the centre current lags the current
at the surface.
If the skin effect is relatively hard to understand, it's even harder to
calculate exactly. There are a couple of approximate formulas that works
fine within certain limits but they don't cover the whole range. It won't
be easy even if you try to calculate it in an exact way because the solution
becomes unstable outside certain values.
This program was made to simplify the calculation for anyone who wishes to
calculate the skin effect of a round solid conductor. It uses the best method
I know of for the moment and gives a very precise answer in every case. The
unregistered program uses an approximate formula that gives an answer close
to the exact solution. It is enough for anyone that roughly want to
know the influence of the skin effect. But if you want an exact calculation
and get all the options of the program you have to register and pay for the
program.
Internal inductance and its frequency dependency:
The inductance this program calculates is the internal inductance in
the wire and should not be confused with the external inductance that depends
on how the conductor is winded or what way the return current takes.
The internal inductance depends on how the magnetic flux is distributed inside
the conductor which depends on the skin effect. That's why the internal
inductance has a frequency dependency and the skin effect is an important
part of en inductance calculation.
Other effects:
Another effect that gives a frequency dependent current distribution
in a conductor is the proximity effect. It comes from external magnetic fields
like that from a return current. The result is that the two current paths
try to run as close to each other as possible. All to minimize the inductance
and the stored energy. Since this effect depends of external geometries it
isn't calculated in this program. |