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What is the basic definition of a tesla coil

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Marko

Mon Feb 18 2008, 08:13PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Tesla Coil = Air core transformer

So if I base drive a resonator it is not a tesla coil any more?

This nomenclature was never clear to me, but I didn't care much either.

Both 'tesla coil' and 'magnifier' are poorly translatable to my language, so as a broad term I simply call it a helical or tesla resonator, and tesla transformer if it specifically has an air cored primary coil.

Oh, and in some rare cases I may have a helical resonator with ferrite core, that's not a tesla coil too I assume?

teslacoolguy

Mon Feb 18 2008, 09:37PM

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my best description of a tesla coil is an air cored resonant pulse transformer

Arcstarter

Tue Feb 19 2008, 04:09AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

if you get what a transformer works like you can easily learn how a tesla coil works.basically what happens is there is a high voltage transformer(i have seen as low as 1000volts and as high as 30000volts.i recommend starting with 6000volts or so.)that charges a high voltage capacitor.when the capacitor charges up enough voltage it will release all of its energy into a coil of typically 3 to 12 turns of thick wire or copper tubing.there is then a magnetic pulse that goes through the coil of few turns.the "primary".the coil with many turns(around 900 to 1200)called the "secondary",which picks up the magnetic field and transfers it into high voltage.to get correct operation you need to have it "tuned" to its "resonant frequency".the tuning can be done by changing or tapping the amount of wire on the primary or changing the capacitance.resonance is like pushing a kid on a swing.when you push at the peak of the backwards stroke you get the kid to swing further.then you have acheived the resonant frequency.if you need to know more just let me know!

Terry Fritz

Tue Feb 19 2008, 05:00AM

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Hazmatt_(The Underdog)

Tue Feb 19 2008, 06:23AM

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Here's my shameless plug:

thermite

Tue Feb 19 2008, 07:53PM

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NeilThomas wrote ...

For deriving the voltage gain, you can ignore the resonance aspects, that's just a mechanism that transfers as much of the energy from primary to secondary as losses allow, and do all the sums through energy.

Given that you know that E=1/2CV^2, and that at the voltage peak all the energy is stored in the capacitance and none in the inductance, then you can work out that the voltage gain (Vsec/Vpri) is just sqrt(Cpri/Csec) (neglecting losses).

BTW, try to avoid "almost infinity" in thinking about problems. For a single resonant circuit *being supplied with power* the voltage at resonance grows until it reaches equilibrium, that is the power loss equals the power supplied. The losses will come mainly from current flowing through resistances, though dielectric and radiation losses may add their tu'pen'th. Not so complex, and not a phasor in sight. Energy again, it's a damned handy concept!

There is one big conundrum with this otherwise very elegant approach.

You have five energy storage elements, two caps and 3 inductors. you must prove that there is a state in the coupled resonator when all the energy has gone to the output resonator from the input resonator. It may be obvious to many of you, but I need a proof. Hell if we are asked ad-nauseum to prove every little aspect of thermate theory of 911, why cant someone show me the shortest and most intuitive (not the brute force) way to understand basically a 5th order system of two weakly coupled LC resonators in this aspect only.

Take a look at the paper linked by goldsphere, where the plots of voltages of C1 and C2 are plotted in the two caps system,

and

in the three caps system he has voltage for all three. The zero crossing of VC2 and VC3 is by the initial condition. The final state is where only VC3 is non-zero.

I hope you see that this is an assumption that still needs to be proven to permit the usage of energy equalization.

Now a practical question:

I can get from somewhere (dont know yet where) a formula for the inductance of a single layer solenoid and also its distributed capacitance. I have a rough formula in mind in which

L is proportional to TPL^2 and also to length and to area

turns-per-length = TPL

can someone give me formula for the distributed capacitance ? and a derivation since this is not easy to find.

The secondary is in the shape of a tower.

What is the shape of the primary ? Pancake ? can it be a short solenoid at the base ? Whart are the pros and cons ?

Can the primary operate without a cap ?

can I make primary similar by keeping LC constant in both ?

Finally, how do I kick the primary from energy using a spark gap ? I dont prefer to use any semiconductor. I also dont want to use an induction coil.

I am a total newbie. I have not seen a video where people run their induction coil and then take covers off and walk you through its anatomy and operation.

Thanks a lot for your help

CT2

Tue Feb 19 2008, 08:41PM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

This strays away from the topic of what defines a tesla coil a bit, but here is a video on youtube i found in about 2 seconds

He covers all the different parts of the coil, pretty informative as he does "take the cover off" and show you everything.

Dr. Slack

Wed Feb 20 2008, 08:24AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

you must prove

hey, chill, relax!

You have five energy storage elements, two caps and 3 inductors

No. A Tesla Coil secondary is not an inductor. If it was, it wouldn't have a 3rd harmonic resonance. It's a transmission line. Approximate single-frequency models give it an effective inductance and self-capacitance.

The paper that Golshpere pointed to is quite clever in its own right, but in its precision, it misses the essence of a TC. In fact it doesn't claim to model a TC, and it does not. The question that the mathematicians ask is "can you get a perfect theoretical system that transfers all of its energy into the output device?", and one answer is that paper.

The question that most Tesla Coilers ask is "can you get a real system that's easy to build and transfers most of its energy to the topload?" and the answer is a whole bunch of Tesla coils of varying dimensions. The essence of a TC is two weakly coupled resonators which start with energy stored in the primary capacitor, and transferred at some point to the effective capacitance to ground of the topload.

It's a physical fact, deeper than the mathematics in that paper, that two coupled resonators will exchange all of their energy back and forth during their cycle. However, the physical complexity of a TC means that any identification of those fundamental resonators with the physical components is only approximate, as they include wiring, stray fields, inter-turn as well as to-ground capacitance. The primary resonator is fairly accurately an LC circuit, so there is little error in simulating this as such. The secondary is a transmission line with a capacitive load, and this is a long way from an LC circuit, although the use of "effective" inductance and capacitance, which is most easily obtained by measurement, allows people to make surprisingly accurate and simple models.

thermite

Wed Feb 20 2008, 07:24PM

Banned on 02/27/2008
Registered Member #1326 Joined: Sun Feb 17 2008, 11:19PM
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NeilThomas wrote ...

you must prove

hey, chill, relax!

You have five energy storage elements, two caps and 3 inductors

I was aware that secondary is a segment of a transmission line, and if you see the other post where i am asking for derivation, each turn has inductance and self capacitance and this is how a transmission line is modelled ... actually not. A transmission line either has a return line (real) or image in a ground plane. The capacitance is always shunt in all the models. so you have to show me a transformation to that model or a reference. If the secondary were lying horizontal on the ground, I would say that it can have dominant shunt inductance. but since it is vertical, that is not major and fixed value. At this time I am not worrying about the termination on the coil, but there is no harm in assuming two plates of a capacitor on each end, and this capacitance is not much bigger than that between closely spaced turns.

Assuming, transmission line model of secondary is correct, lets see if there is a mathematical way to model an LC resonator coupled to a transmission line and follow its dynamics. a picture is needed to show the geometry. Intuitively its obviously like a laser or maser. an excited atom is a resonator, though not exactly. the transmission line with reflections of wave is like the ruby rod with end reflections.

This modelling can be very enlightening and satisfying or else there is an endless mental loop of doubts.

and I am chill and cool when it comes to analysis or you cant handle the 911 theories and jump to media given conclusions like a hot head ... so consider me a cold-blooded analyst.

cheers

c4r0

Wed Feb 20 2008, 08:13PM

Registered Member #151 Joined: Sun Feb 12 2006, 02:53PM
Location: Poland
Posts: 153

Terry Fritz wrote ...

This video was on the TDUs website but it disappeard from the server.

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