Re: Questions for the simulators.
Subject: Re: Questions for the simulators.
From: Terry Fritz <twf-at-verinet-dot-com>
Date: Sat, 02 Jan 1999 19:11:19 -0700
I have simulated a few things :-))
At 01:14 PM 1/2/99 -0600, you wrote:
>Bart, your data is beautiful, I just wish it included more coils that
>deviate from the norm. As for shaping the secondary, I give an hour glass
>only as an example. My thought is that the shape of the coil could be used
>to improve the field shaping for the purpose of increasing the maximum arc
>length possible before secondary breakdown. From my brief readings on HV
>pulse transformer design I gleaned that sharp field gradients near the
>secondary windings are not desirable. Perhaps someone could use a field
>solver to explore the possibilities(Jim??? Any other takers?).
The turn to turn field stress are greatest in the bottom of the coil and
lessen toword the top. However, the space just a inch or so out form the
coil sees higher stresses nearer the top than the bottom. So the turn to
turn voltage is not the problem, it is the high E-fields adjacent to the
coil that gets secondary arcs started.
I am working on a program that calculates the voltage fields around a
given coil configuration. It then writes a data file that excel or some
other program can use to plot or manipulate the data. The program is
designed to find the Fo frequency of a given coil configuration but it has
very powerful internal processing that can do field maping as a sideline.
Compared to finding Fo, E-field maping is trivial.
I did other maping work long ago but stopped because I didn't know enough
about the terminal voltages and voltage distribution along the secondary.
However, now I have the information I need, this work has started again.
This maping is really neat and much can be learned about the field stresses
around a Tesla coil. It also makes really neat pictures :-)
The program will run under DOS (or a virtual DOS window) on any PC (even
the original). However, a 500MHz quad XEON machine is preferred due to the
time it takes to calculate all the data... :-)) It is in QBASIC but once
it is figured out it should be easy to convert to a faster language
(hopefully, by someone who knows how to program :-)). If you are
interested in getting the sub-alpha verion let me know and I'll send it
your way. It does field outputs right now. You will need Excel97 or some
program that can display a text file with a big (100x100) array of numbers
in contour plots. Preferably color 3-D.
> Another possibility would be a secondary that transitioned from a flat
>spiral to a cylinder. A highly coupled coil could be made without the
>breakdown risks of a cylindrical secondary inside a conical or helical
>primary. This arrangement would be like a hybridized pulse transformer and
I have experimented with coils that are wound in a non-linear way. Close
winds near the top and far winds near the bottom. This was to help even
out the field stress along the secondary. This early work is reported at:
See the HTML page about non-linear coils.