RE: Top Capacitance Dominant?

Terry -

Another possibility is that the toroid loses capacity when it is mounted on
the secondary coil. This would mean the coil self capacity is more than 3
pf. In an earlier post I said the toroid looses 15 to 20 % of its free space
capacity when placed on the secondary.

A few years ago I read somewhere that a typical single wound TC coil would
lose most of its self capacitance if the windings were spaced more than 31
mils apart. Could this be one of the reasons why Tesla built the CS coil
with about 3 inch spacing? The Medhurst equation does not even use windings!

John Couture


-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, April 29, 2000 7:44 PM
To: tesla-at-pupman-dot-com
Subject: Top Capacitance Dominant?

Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>

Hi All,

	I ran the E-Tesla5 I modified for Bob on my coil.  Of the 18.13pF of
secondary capacitance, the program says 15.16pF of that is in the top
terminal!!  Perhaps this is why TC's with terminals and lumped models like
each other so much.  If the vast majority of the capacitance is a big
"lump" at the top of the coil, the transmission line fun a long the
secondary may not be very significant.  This only leaves 3pF for the
secondary putting the "line frequency" at 618kHz and the 1/4wave time at
400nS when my coil should have a 1000nS delay (250kHz) which really does
seem to match the real case.   Hmmmmm...  Not sure what it all means but it
means something...  May be fun to do that square wave test with a terminal
on the coil...

Pounded the rocks just about into dust now... ;-))