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Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
What is likely to be the effect if I was ti implement a a radial counterpoise ground plain on a circle of artificial grass and connect that ground to a spike in close proximity to a spike coming off my torroid?
Compared to connecting that radial ground plain to a metal spike driven into damp earth to a depth of about 50cm?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
It would behave as if the radials were a real earth provided that the capacitance of the counterpoise radials is many times greater than the topload capacitance. If the radials capacitance is low it will still work but pri-sec flashovers may occur due to the voltage at the bottom of the secondary.
Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
Sulaiman wrote ...
It would behave as if the radials were a real earth provided that the capacitance of the counterpoise radials is many times greater than the topload capacitance. If the radials capacitance is low it will still work but pri-sec flashovers may occur due to the voltage at the bottom of the secondary.
I am thinking a more practical way would be to obtain a roll of 1.2m high chicken wire and unroll it to form a cylinder of diameter about 3 times the height of my coil.
This would be far more convenient that trying to flatten chicken wire on the ground or attach lengths of copper wire to a circle of artificial grass.
How would you know if the capacitance of such an arrangement is many times greater than the top load? Not easily I suspect.
Perhaps it is better to connect my cylinder of chicken wire to an earth rod.
Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
Sulaiman wrote ...
yes
Some one should create a detailed page on this particular aspect of Tesla coils including specifics on areas appropriate to secondary coils sizes, materials, ground rod versus counterpoise pros and cons,......
I have only manged to find bits and pieces and general info on the subject but nothing really that gave me the confidence to say yes I will create my ground that way.
If this sort of earth is appropriate for my tesla coil then what would it take to make this type of earth inappropriate in my situation and an embedded earth rod preferable?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
That counterpoise looks great.
From a connector somewhere on that mesh, run a wire to the bottom of your secondary, or the bottom of the secondary I sense current transformer, and to your TC power supply mains ground. If you are going to operate the TC in that position, then a radial out to your garage door would be good. Are there any other significant areas of conductor that either might get hit by streamers or present a large capacitance to the topload (like steel joists above our head out of shot)? If so, run a radial to them as well.
Thinking about a detailed page, maybe three illustrations would do it. On one extreme, a TC operating in the middle of a field, with secondary bottom connected to the ground. On the other, operating inside a Faraday cage, with secondary bottom connected to the floor of the cage. Then a third showing how any real situation is usually somewhere between the two. But always, the plan is to get the current back from things that are capacitively coupled to the topload back to the secondary bottom terminal, without undue inductance, and without producing inadvertent large voltages between innocent bystander conductors.
Depending on your operating position, the real earth may, or may not be, a conductor that has significant capacitive coupling to the topload. If it is, then connect to it by the shortest means, whether that's an earth spike, or your mains protective earth. If it isn't, then forget about it.
The nice thing about a counterpoise is that it's an organising principle, as much as anything. It's a cheap and easy to provide terminal that does have much coupling to the topload, and it's in the right position to connect with a short wire to the secondary, and back to the TC PSU ground. You'd connect any arc target to it as well. Then having done that, you look around. What else does the topload see? Garage door? Radial to that.
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