RE: Where am I going askew ?

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

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


Christopher -

You may want to try the JHCTES Ver 3.42 computer program. This program is
simple and easy to use and is based on the Wheeler and Medhurst equations.
The program will give you outputs that will be the same or close to JAVA10
which is a more complete program.

Enter the following:

Primary - .00536 - 8.0 - 8.5

Secondary - 2.25 - 1000 - 44 - 0 - 22.0

Press "Calculate" and get outputs

Fres = 200.59
Pri turns = 17.00
Sec inductance = 20.45 mh
Etc, etc.

You can change any of the inputs and when you press "Calculate" the computer
will do the calcs and give you inputs/outputs that are always in tune. I
agree that the primary capacitor should be larger. When you change the
primary capacitor in the program and click "Calculate" you will get all of
the new parameters for a Tesla coil that will be in tune.

The program is an on-line program and can be found at

    www.mgte-dot-com

Click Tesla, JHCTES (Books), etc.

Note that if you used #24 AWG for the secondary wire you can find the
"inductance" of your secondary by measuring its "resistance" in ohms and
using the JHCTES program. Divide the resistance of your secondary (about 30
ohms) by .02617 ohms/ft and you will get about 1000 feet. Just adjust the
JHCTES secondary inputs to give you this total wire length in the outputs.
The output inductance will then be the inductance of your secondary as
determined by the Wheeler equation. Of course you can do this neat trick for
any secondary wire size if you know the ohms per ft of the wire. The JHCTES
program is full of tricks.

John Couture

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


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, October 24, 2003 11:37 PM
To: tesla-at-pupman-dot-com
Subject: Re: Where am I going askew ?


Original poster: Bart Anderson <classi6-at-classictesla-dot-com>

Hi Ed,

 >Christopher,
 >
 >I read Bart's reply on your questions.  I also ran some calculations on
 >your coil but for some reason, came up with different numbers than Bart
did.
 >
 >(Bart, the primary difference seems to be in the resonant frequency of the
 >secondary.  I used 49.75 turns / inch and at a 97% winding factor - i.e.
 >we don't usually achieve a turns per inch as tight as in the wire
 >tables.  I get 1,086 turns total.

Ed, using 24 gauge wire (which is what was used), Javatc calcs 44.4
turn/inch. 24 gauge is 0.0201' bare and 0.0012" insulation (single build).
This is nominal magnet wire values from Phelps-Dodge tables. If anything,
44.4 TPI is on the tight side. In the real world, a closewound coil will
typically end up with less which can be put on the shoulders of
human/machine error and tensioning affects. This of course will decrease
the number of turns per unit area. Your 49.75" is extremely tight for 24
gauge wire (unless the wire is far outside of nominal values). Possibly you
used some other gauge?

That is one factor of of why your Fres is lower. The other factor is your
loaded C value (your program is probably seeing 9.3 pF Cself and your
probably using 21pF for topload, and then lumped together). What your not
putting into the mixing bowl (and can't very well in Excel) are the affects
in capacitance when the coil is in proximity with toroid at their positions
above ground and the affects of current distribution at Fres (which becomes
more uniform with addition of the toroid, but in this case, still has a way
to go). Fantc would be the a place to take a look at current distribution
(the VI profiles are an output of the Fres Analysis). I've also made a
change a while back to output the VI profile length's to the input units
(inches, meters, etc.), so it should make a little more sense to the user.

Here are a couple graphs using Fantc's VI profile data. I simply copy/paste
the numbers to notepad, opened delimited in Excel, and plotted the graphs.
Both Fantc and Javatc use VI profile data. I've chosen to leave out this VI
output from Javatc as it is more inline with Fantc's analysis style as
opposed to Javatc's design style.

The current is based on a 1 amp nominal value and are the mean values over
the length of the corresponding element. These of course would need to be
scaled to actual base current measurements.

http://www.classictesla-dot-com/temp/vi_loaded.gif

http://www.classictesla-dot-com/temp/vi_unloaded.gif

Take care,
Bart

 >   Using a 4.5" secondary with 22.5" winding length, and a 4 x 20" toroid,
 > I get a loaded frequency of 184 khz.  Much lower than your
 > calculations.  I am sure my program is not nearly as accurate as Javatc,
 > but it usually works good for me.)
 >
 >With a 6.5" I.D. on the primary, I calculate 19.2 turns needed on the
 >primary.  Even if it is only 16.4 as Bart calculates, that is getting to
 >be a good sized primary.  For this reason, and that .005 ufd is just about
 >resonant with your transformer, I would suggest going to a larger
 >capacitor, like .01ufd.  The primary would then tune when tapped at 14.6
 >turns - according to my calculations.  I do agree with Bart on the
 >selection and design of the secondary.
 >
 >Ed Sonderman
 >
 >