RE: Toroid Capacitance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John H. Couture by way of Terry Fritz <teslalist-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


Terry -

The toroid capacitance reduction will always be a guesstimate at the TC
design stage because of it's nebulous nature. The reduction is caused by
surroundings that have unknown variable electrical capacitance effects and
the effect of these variables on the toroid can only be approximated. The
reduction changes every time the surroundings change and this changes the
resonant frequency.

Why should a coiler care about the toroid reduction? It should be noticed
that the capacitance of the toroid has some effect on the output spark
length. Ignore the toroid reduction and you get less spark. The larger the
toroid capacitance the higher the voltage and the longer the spark.

I have also found that one of the apparently easiest TC tests is to
determine the resonant frequency of a TC after it has been built. However,
the accuracy of the test can vary over a wide range. Before toroid
reductions and resonant frequencies will make sense a standard method of
testing for the resonant frequency will have to be established.

Because all TC programs can only approximate the toroid capacitance
reduction at the time the TC is being designed the effective toroid
capacitance and the resonant frequency in the program may or may not have a
large error. At present the Paul N. TSPP appears to give the most accurate
results.

The JHCTES program resonant frequency in the outputs depends on the TC
designer's estimate of the Secondary Terminal input to the program so the
accuracy can vary. If the designer is experienced and very lucky the toroid
reduction and the resonant frequency could be 100% accurate, however, the
odds are high against it. One way to improve this program accuracy is to use
the data you can get from Terry's E-Tesla6 program and add it to the JHCTES
program.

Bart Anderson and I are working on making the JAVATC program the best
available for designing Tesla coils. This program has worked very well in
the past, however, at present like all other programs the toroid reduction
is the weak link. We expect that this will be improved by using the TSPP
program.

John Couture

-------------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, July 19, 2003 6:18 PM
To: tesla-at-pupman-dot-com
Subject: Re: Toroid Capacitance


Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi John,

The capacitances of toroids, coils, and their combination is well known and
understood.

If one takes say a 20pF (free space) toroid and adds it to a coil with a
Medhurst capacitance of say 15pF, The combination will (in fact must) have
significantly less capacitance.  Maybe like 27pF.

All these can be calculated with E-Tesla6:

http://hot-streamer-dot-com/TeslaCoils/Programs/Programs.htm

Cheers,

          Terry

At 05:52 PM 7/19/2003 -0400, you wrote:

 >All -
 >
 >Have any coilers found that the Toroid free space capacitance is reduced
 >when the toroid is placed on the secondary coil?
 >
 >John Couture
 >
 >-----------------------------------