Re: [TCML] MAX SPARK FOR FIXED VOLTAGE

[DC Cox <resonance@xxxxxxxxxxxx>]

Bart has delivered lots of good info here.

Keep the power as high as practical (putting multiple nsts in parallel) and
when doing initial design: (1) keep the sec coil's radius as large as
practical, and (2) ensure efficient spark gap quenching (my favorite is the
hyperbaric gap for excellent performance with neon transformer powered
systems).

Many happy long sparks!

Dr. Resonance




On Tue, Mar 10, 2009 at 7:24 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:

> Hi Dex,
>
> Your question is good, but it is based on the assumption that potential
> voltage equals a given spark length. This isn't the case in a Tesla coil
> output spark like it is in the potential required for 2 bodies of some size
> and geometry to arc to one-another. Over and over again it's been shown that
> spark "lengths" in TC service follow a power curve. It depends on the power
> delivered to the streamers and time. The actual voltage at the top load
> cannot be directly linked to spark length without the inclusion of the
> change in current over time. The main parameters that supply this are the
> inductances, capacitances, power supply, and top load limit on voltage.
>
> A better question and answerable question is what is the approximate max
> spark length possible for a given power. Then we can easily quote John
> Freau's 1.7 x sqrt(input watts) spark length equation which has held well
> for more than a decade. There are certainly situations which affect even
> this spark length, but it is the most accurate equation for spark lengths
> over the spectrum of variations with systems.
>
> I can accurately say that if you used 100kV, 200kV, 300kV and kept power
> unchanged, then for a 1000W coil, expect the following ideally.
> 1) 100kV = 53.7"
> 2) 200kV = 53.7"
> 3) 300kV = 53.7"
>
> This is not a trick. It states that the terminal voltage is not affecting
> the spark length directly. Maintaining power delivered to the spark at
> 1000W, the current is adjusting (10mA, 5mA, 3.3mA). However, if you were to
> double the power to 2000W, then (ideally):
> 1) 100kV = 76"
> 2) 200kV = 76"
> 3) 300kV = 76"
>
> Note the spark length increased only by a ratio of 76/53.7 for twice the
> power. This is the reality of Tesla Coils. BTW, by "ideally" I'm referring
> to the fact that not all coils will achieve the spark lengths for the power
> given. Most will be below this length, some at this length, and a select few
> a little better (John's system during these tests were quite efficient).
>
> Another reality not thought about is that you will be hard-pressed to keep
> the top terminal below 100kV and above 400kV. The top terminal limits
> voltage but can also break out at peak voltages which are far from average
> voltages. From a completely academic standpoint, it's fine to contemplate
> the top terminal voltage, but for breakout, consider the peak voltage the
> top terminal will see (punching out). However, after the initial breakout,
> the current delivered to the streamer is what will dictate to some degree
> the spark lengths achievable. The power is what pumps the current into the
> spark channel (and the more power, the longer and higher the current is
> available).
>
> I can probably speak for a lot of coilers when I say that reducing gap
> losses (more power delivered in the emf at the primary and thus the
> secondary) and more power in the supply itself is what has increased spark
> lengths on any given coil. There is of course secondary inductances better
> equipped than others at delivering the power to the top terminal and the
> terminal C itself determining when breakdown occurs, but it is "power" that
> ultimately delivers short or long sparks (power is the predominant player
> with spark lengths).
>
> Take care,
> Bart
>
>
>
> Dex Dexter wrote:
>
>> I have a good question I don't know answer to.
>> QUESTION:
>> What is aproximately maximum spark lenght possible for a given output
>> voltage Tesla system generates?
>>  Regardless of the efficiency,how long spark can be produced by a
>> Tesla-type impulsive devices with voltage levels:
>> 1) 100 kV
>> 2) 200 kV
>> 3) 300 kV
>>  Can a high power impulse source,like a Tesla transformer,put out a 10
>> feet long spark with 'only' 100 kV voltage peaks?
>> To accomplish that it is free to use any power input level,any size and
>> shape of  a terminal capacity,any firing rate wanted,andthe best high
>> frequency excitation waves mix.DRSSTC,VTTC,etc.
>> The only limiting thing is not to exceed 100 000 V terminal potential.
>> Supposing a normal atmosphere enviroment is that possible?
>> I know that in no circumstance 50 kV can close 5' wide gap unless directly
>> conducting path is formed somehow,or a
>> strong external ionization occurs ,like exposure to a flame,extremely
>> powerful lasers,but Tesla transformers are the champs of 'spark pumping' and
>> I was wondering what could be done with 100 kV.
>> Thanks for  your answers and explanations.
>>  Dex
>>
>>
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