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Re: [TCML] MAX SPARK FOR FIXED VOLTAGE
Bert,I think you understood ,almost completely,my question.
The essence of the question is giving higher and higher number of
pulses per second WITH SAME BANG ENERGY to Tesla coil and see how
spark grow.With quite a big topload capacity the peak voltages will
be about same after each bang (actually they will decrease a little).
At what PPS rate sparks stop to grow longitudinally given output voltage?
3000 PPS?
4000 PPS?
5000 PPS?
More?
There must be a limit for spark lenght given optimum HF excitation for each voltage level.
To clarify my question to the others.
My question is NOT power efficiency related.Since folks like numbers I'll give an example.
If necessary use 100 kW DRSSTC and 10000 PPS to reach 10 feet with a big coil ,but with only ~100 kV output peaks.
I'm quite certain spark of such lenght can't be produced with 100 kV,no matter how much power used.
Dex
--- bert.hickman@xxxxxxxxxx wrote:
From: Bert Hickman <bert.hickman@xxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Cc:
Subject: Re: [TCML] MAX SPARK FOR FIXED VOLTAGE
Date: Wed, 11 Mar 2009 20:52:29 -0500
Hi Dex,
Unfortunately, there are no simple answers to your question. The quest
for maximum spark length has been the coiler's Holy Grail for well over
100 years. However, even the very best available modeling tools, such as
Bart's JavaTC or FANTC, model electrical behavior for _non-sparking
Tesla Coils_. Although they can model the voltage at which initial
breakout should occur, once sparking begins about the best we can
currently do (regarding spark length) is to estimate "best case" spark
lengths using John Freau's empirically-derived power-spark length
relationships for the type of coil and operating mode.
This is not from a lack of trying. It's from a lack of usable dynamic
leader/streamer models that can be used with the repetitive complex
waveforms of Tesla Coils.
In a nutshell, we don't understand precisely how resonator and topload
energy "couples" to attached sparks. Or how topload and resonator
parameters relate to spark propagation. Or how spark length is
individually or cumulatively affected by frequency, resonator impedance,
topload capacitance, topload ROC, peak output voltage, break rate,
coupling coefficient, or bang size. Nor do we know how to accurately
model the dynamic, nonlinear, distributed, and random branching nature
of Tesla Coil leaders and streamers, or the effects of residual space
charges, or residual channels left by previous bang(s). It is clear that
simple lumped models, SPICE, or other lumped circuit modeling tools
alone will not be up to the task.
Frankly, I don't foresee this situation changing any time soon. There is
very little scientific interest in Tesla Coils. Those few areas deal
with heavily coupled, non-sparking resonant transformers for pulsed
power applications or educational demonstrators. Practically speaking,
the only folks who actually study Tesla Coil sparks to any degree are a
small subset of hobbyist and professional Tesla Coilers. The majority
are hobbyists simply trying to achieve maximum spark length for their
systems.
Now, back to your question:
I have no doubt that, given the same resonator and break rate, with
toploads that are scaled to break out near their planned maximum
voltages, then the longest sparks will occur with the 300 kV system, the
next longest with the 200 kV system, etc. Further, spark lengths will
scale as the square root of input power, and the most efficient systems,
(such as DRSSTC's) will provide longer sparks for the same input power.
But I can't tell you what the maximum theoretical length might be, nor
(besides a lot of design rules of thumb) how best to achieve it.
Bert
Dex Dexter wrote:
> Hi,
> Thanks for the answer.
> I'm not interested in losses as already said.
> Neither I'm interested in low repetition rate operation.
> I'm interested in a VERY high repetition rates with fixed
> primary energy what (roughly) gives fixed output voltage.
> If necessary ,4500 pps to be used with 100 khz solid state
> system.
> To clarify,you basically say that with generated ~100 kV secondary peaks
> it's not possible to get more than 5 feet discharge no matter what you do?
> What would be aproximate maximum for ~200 kV?
>
> Dex
>
>
> --- resonance@xxxxxxxxxxxx wrote:
>
> From: DC Cox <resonance@xxxxxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Cc:
> Subject: Re: [TCML] MAX SPARK FOR FIXED VOLTAGE
> Date: Tue, 10 Mar 2009 17:22:17 -0700
>
> Output potential is Vsec = Vpri (peak) x 70% x SQR(Lsec/Lpri).
>
> Also max potential is a function of inductance, whereas: Vsec = L x dI/dt
> (rate change of current with respect to time).
>
> Inductance goes up as the square of the radius of the sec coil, and
> generally large inductances produce higher potentials.
>
> Spark length depends of total power and also the repitition rate (pps) of
> the spark gap and it's ability to properly quench at the power level
> being used. Once a large volume of ions are created above the HV terminal,
> then it's a "pumping action" every time the sec fires into this ion cloud.
> The residual ions help to make the spark "grow" in length even though the
> potential is lower.
>
> It's quite possible to get 4-5 ft sparks at 100 kV IF the power level and
> rep rates are high enough. As an example a typical coil running 450 pps on
> the break wheel, with a 100 nF capacitor (0.1 uF), runs a true 1 million
> volts with a 14 ft. long sec spark.
>
> Again, rep rate, power levels, and efficient quenching are required to
> produce high performance even at lower potentials.
>
> Solid state coils exceed these performance levels due to their highly
> efficient switching and lack of losses used to heat the spark channel in a
> standard
> type spark gap.
>
> If you operate any Tesla coil in a single shot mode, firing once every 15
> seconds, then this spark length is a very accurate indicator of the coil's
> maximum output potential. It agrees with the equations I have listed above.
>
>
>
> Dr. Resonance
>
> On Tue, Mar 10, 2009 at 11:37 AM, Dex Dexter <dexterlabs@xxxxxxxxxxx> 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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