[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Thumpers Toroid - general ring-toroid modeling
Finn and all,
Some background:
Steve Ward and I had similar discussions in early 2009 regarding
multi-ring toroids, prompting me to do a bit of investigation. A precise
solution for "bundled conductors" requires field modeling software.
However, there is a closed form approximation that provides a fairly
accurate estimate (~5-7% error) for the maximum surface gradient for
bundled conductors used in HV utility power transmission lines.
The equations I started from were taken from the ABB Switchgear Manual,
10th edition, section 4.3.3. This was then modified appropriately for a
single "monopolar" line elevated above ground (a type of HVDC power
transmission line design). For those with access to the literature, the
modeling technique was originally published in a 1948 paper by M.
Temoshok, "Relative Surface Voltage Gradients of Grouped Conductors".
Numerous other references can be found by Googling for "surface field"
and "bundled conductors". For convenience, the modified model for
bundled transmission lines is contained within the following
spreadsheet. Input parameters go into cells C6 - C13. This can provide a
ballpark estimate for roughing out paper designs of ring toroids:
http://www.capturedlightning.com/Papers/Bundle.xls
Now some BETTER news:
Antonio Carlos M. de Queiroz's Inca program can conveniently handle ring
toroids from inputs generated by the above spreadsheet. Manually
entering individual conductor coordinate and parameter data can
otherwise a real pain for multi-element toroids with finite conductor
diameters. The Inca program can be downloaded from Antonio's site:
http://www.coe.ufrj.br/~acmq/programs/ (all of his programs)
http://www.coe.ufrj.br/~acmq/programs/inca.zip (Inca)
In the Bundle.xls spreadsheet, enter the ring-toroid data (in feet and
inches) in Cells C8-C15. Inca models conductors using discrete wire
rings, and if you try to use too many rings/bundle or too many bundles,
Inca may complain about having "Too Many Rings". By reducing the number
of rings/conductor to 10 (Cell N14), you can enter up to 36 bundle
conductors - this should be sufficient for most Tesla Coil toploads. Try
to use the largest number of rings/conductor to get best accuracy.
Before actually computing in Inca, you may want to set the
"Electrostatics - Parameters" for Vbreakdown to 2600 kV/meter instead of
the default value of 3000. Then, select "Electrostatic Calculations",
and select "General Case with Axial Symmetry". Copy and paste
spreadsheet cells W16 down (for the number of bundle conductors)
directly into the data entry General Case window of Inca (upper left
window) and press "Calculate". This approach allows you to conveniently
simulate a wide variety of ring-toroid designs. You can also compare
Inca's results to the Utility transmission line model (left half of the
spreadsheet) for an isolated bundled transmission line (Cells C17 and
C18). The utility surface field estimator is convenient for getting into
the ballpark before running a complete Inca simulation, but it has lower
accuracy.
Once you've completed the Inca calculation, you may wish to plot the
potential and total electrical fields for the calculated geometry. You
may be able to obtain even better accuracy in Inca by adding a ground
plane to the model. Or, it may be easier to use Bart Anderson's JAVATC
or FANTC to do this, using the a regular toroid of similar overall
dimensions and adding the secondary, ground plane, and/or walls.
Following is a screen shot of the potential and total E-fields from an
Inca simulation that assumed 26 kV/cm for breakout and a very large (9
foot diameter) toroid consisting of 16 1.5" diameter rings, with a minor
(or bundle) diameter of 18". For this model, Inca predicts a toroid
breakdown voltage of about 1.146 MV, while the utility transmission line
model predicts 1,028 MV. The following screen shots show the ring-toroid
model and calculations and the plot of total electric field:
http://www.capturedlightning.com/Papers/Bundle-Toroid1.jpg
http://www.capturedlightning.com/Papers/Bundle-Toroid2.jpg
Hope this may be useful and best wishes,
Bert
--
********************************************************************
We specialize in UNIQUE items: coins shrunk by ultra-strong magnetic
fields, Captured Lightning Lichtenberg figure sculptures, and scarce
technical Books. Please visit us at http://www.capturedlightning.com
********************************************************************
Finn Hammer wrote:
Phil Tuck wrote:
I am considering a tubular example like Finn's recent "Thumper has
utilized.
How does the ROC of these toroids relate to the level of charge they
can retain?
Snip
Just a last thought but all of these I have seen are on DRSSTC or
other SS stuff, are they just as usable on old style RSG 80 Khz
technology or do they prefer a high frequency coil?
Charge contained is very close to solid type, which means that we arrive
at the same expected capacitive load as calculated with JavaTC,
breakdown voltage is unknown to me.
Greg Leyh might tune in here, since he introduced this type of toroid to
the coiling segment of high voltage. I have seen similar (well, slinky
type, really ) constuctions in pictures of russian power plants, so
perhaps there is russian litterature about this subject, but where is
Father Dest these days?
Bert Hickman, master of the litterature, Help us out here!
With relation to preferred frequency of operation: Thumper is resonating
around the 35kHz mark.....
Cheers, Finn Hammer
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla