Author Topic: Counter Poise Grounding for Tesla Coils  (Read 364 times)

Offline UweD

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Counter Poise Grounding for Tesla Coils
« on: September 17, 2017, 02:31:53 PM »
Dear All,
I have a few questions concerning counterpoise grounding for Tesla coils.

- Is this type of grounding capacitive or inductive in nature?
- Can it be tuned?
- Can the counterpoise ground be completely disconnected from the mains ground?

I look forward to hearing from you.
U.

Offline Mads Barnkob

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Re: Counter Poise Grounding for Tesla Coils
« Reply #1 on: September 18, 2017, 07:35:04 AM »
1. You have evaluate your counter-poise as capacitive in order to compare it with the capacitance of your coil. The counter poise will look like a real ground if the capacitance of the counter poise radials/sheets is many times greater than the topload capacitance. If the counter poise capacitance is low, it will still work, but primary to secondary flashovers may occur due to the voltage buildup at the bottom of the secondary, due to equal capacitances in both ends of the coil, basically you would get a very unbalanced bipolar tesla coil.

2. There certainly are situations where the ground impedance can be too low, or too well "tuned" for high current performance in some way. Where your dishcharge current is so high and rapid that a voltage wavefront can move faster down the secondary than it can handle and previously experiences show that the bottom 20% of a secondary coil could suddenly just flash over and explode, this is from people that have use too good counter poise grounds with low impedance. This thread properly has the best recorded information about this subject: http://4hv.org/e107_plugins/forum/forum_viewtopic.php?162582

3. yes, a correctly made counter poise ground should be a substitute for another ground connection.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline UweD

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Re: Counter Poise Grounding for Tesla Coils
« Reply #2 on: September 18, 2017, 11:18:06 AM »
Mads, thanks for your reply.

If the ground if capacitive, does it necessarily have to be greater in size (area) than the top load, or should it just be able to carry more charge than the topload?

I read somewhere that a way of creating a counter-poise ground for an antenna is to make use of a 1/2wave resonators. If i assume Tesla secondary is 1/4wave, would that mean a ground consisting of "secondaries" tuned to 1/2 the resonant frequency of the actual secondary would work?
U.

Offline UweD

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Re: Counter Poise Grounding for Tesla Coils
« Reply #3 on: September 19, 2017, 10:19:37 PM »
I guess the more important question to ask is how does one test if the counter-poise ground is adequate?
Any ideas how one may test this?
U.

Offline Mads Barnkob

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Re: Counter Poise Grounding for Tesla Coils
« Reply #4 on: September 20, 2017, 07:27:07 AM »
Here are some links that I collected long ago, but never really got around to read in dept. Hopefully you can find your answer here.

Here are some interesting papers on earth resistance, impedance, skin depth etc:
Theory but some missing pictures:
https://archive.epa.gov/esd/archive-geophysics/web/html/factors_influencing_electrical_conductivity.html

Lots of practical measurements and data in tables for TC frequencies http://hal-ineris.ccsd.cnrs.fr/docs/00/97/61/57/PDF/2004-154_hal.pdf - seems like a newer version of the same: http://www.bicsi.org/pdf/presentations/winter_11/Design%20of%20a%20Low%20Impedance%20Grounding%20System%20for%20Telecom%20Applications%20-%20Mitchell%20Guthrie%20and%20Alain%20Rousseau.pdf

Seems similar as the above, but in Italian: http://tesi.cab.unipd.it/39557/1/tesi.pdf

Another ground vs lightning study: https://www.researchgate.net/publication/3763541_Behaviour_Of_A_Grounding_System_Under_Impulse_Lightning_Current

Measurements by a HAM operator: http://www.vlf.it/ed/earthprobes.html

edit: fixed old dead links with their new current url, "#ยค&/( webmasters that does not contain permanent links!
« Last Edit: September 20, 2017, 07:32:42 AM by Mads Barnkob »
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Offline Uspring

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Re: Counter Poise Grounding for Tesla Coils
« Reply #5 on: September 21, 2017, 11:44:07 AM »
UweD wrote:
Quote
I guess the more important question to ask is how does one test if the counter-poise ground is adequate?
Any ideas how one may test this?
You could leave the whole secondary tank floating, i.e. connect the secondary ground only to the counterpoise and then measure the voltage of the counterpoise against the household ground. I'd stronly advise against this, though, since the counterpoise might attain a voltage of many kV depending on its contact to the floor. I once forgot to ground the secondary base properly and arcs shot out from the base. Luckily not much more happened to my coil then the power switch going up into flames.

Offline Mads Barnkob

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Re: Counter Poise Grounding for Tesla Coils
« Reply #6 on: October 09, 2017, 09:08:36 AM »
UweD, I would really like to hear about your results, failures and conclusions on this subject, as it is also a part of my DRSSTC guide on the chapter of grounding.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline UweD

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Re: Counter Poise Grounding for Tesla Coils
« Reply #7 on: October 12, 2017, 12:16:06 PM »
Mads, i will try Uspring's idea of measuring the voltage difference between the counterpoise and the mains ground to see what the effect is of different counterpoise constructions. I'll try by putting a small highvoltage neon bulb in series. The intensity of the glow should give an indication of the performance, right?

Also, found some helpful info in an old tesla coil book by Duane Bylund on constructing counter poise grounding systems. Basically it uses a star pattern of insulated wires radiating outward from the secondary ground. This system couples capacitively with the natural ground.
U.

Offline Mads Barnkob

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Re: Counter Poise Grounding for Tesla Coils
« Reply #8 on: October 16, 2017, 09:32:08 AM »
Lots of practical measurements and data in tables for TC frequencies http://hal-ineris.ccsd.cnrs.fr/docs/00/97/61/57/PDF/2004-154_hal.pdf - seems like a newer version of the same: http://www.bicsi.org/pdf/presentations/winter_11/Design%20of%20a%20Low%20Impedance%20Grounding%20System%20for%20Telecom%20Applications%20-%20Mitchell%20Guthrie%20and%20Alain%20Rousseau.pdf

From this I understand the reasoning for making a grounding system with a high capacitance, to lower the impedance at higher frequencies, but a insulated conductor would just flash over at Tesla coil peak currents, or is it with the end of the rod exposed to ground? Such a rod would also just have higher inductance.

At-least a radial outlaid counter-poise should be underground and not directly hit-able for streamers, then there is no/little grounding, but just termination of the secondary circuit, which I believe has lead to many secondary failures to "Whiplash" effect.

Large plates or band is a more effective way to increase capacitance to ground and low resistance. But really a very short path from Tesla coil base to ground rod is properly the most important to lower voltage peaks due to inductance.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

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Re: Counter Poise Grounding for Tesla Coils
« Reply #8 on: October 16, 2017, 09:32:08 AM »

 


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