Skin effect (was:Primary and copper)

From:  Antonio C. M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
Sent:  Thursday, April 02, 1998 10:35 PM
To:  Tesla List
Subject:  Re: Skin effect (was:Primary and copper)

Jim Lux wrote:

> For a close wound coil, I suspect that you could, at some level, treat it
> as a long cylinder of copper with the current flowing around the cylinder.
> In this case, the adjacent turns "shields" the conductor of interest,
> reducing the effective cross sectional area.

This makes sense. Probably with an "effective angle" in the conducting
tube at the wire surface where there is current. This angle would vary,
being large when the skin depth is small and small when the skin depth
is large. I will verify with an electromagnetic simulator, if I find one
that can compute this (I have used the Qfield simulator for some problems,
with reasonable results).

> FWIW, has any one tried modelling a tesla coil using something like NEC to
> do a complete EM simulation?

The complete simulation of a coil with hundreds of turns is something
rather complex. The FDTD simulator in the APLAC circuit simulator has a
command to define a thin helical conductor that may be usable in Tesla
coil simulations (I haven't tried yet, and expect problems with a large
coil). A limited version of the program can be downloaded through the WWW.
Antonio Carlos M. de Queiroz