From: John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
Sent: Friday, January 30, 1998 8:25 PM
To: Tesla List
Subject: Re: Voltage/Length (fwd)
Malcolm, All -
So now we have a spark length from 3 ft to 9 ft representing one million
volts for the Tesla coil output. If you combine this information with
information from many other coilers as I did and develop the equation shown
below you will find that about 5 ft represents one million volts. I admit
this is a speculative assumption but that is due to the nature of the
coiler's speculative tests.
A single counter example will give a negligible change to the above.
Note that different primary energies and break rates are not involved. We
are talking only about spark length vs voltage. Adding more parameters only
clouds the issue.
By engineering magic I mean engineering that is unfamiliar to people that
are not engineers. Tesla coils can produce some strange (magic) outputs.
It isn't a matter of garbage in, garbage out, it is a matter of properly
applying the various TC equations using a calculator. That is why I believe
the Tesla List should use more equations and examples when discussing TC
engineering. It makes it easier to understand as compared to those abstruse
By "one shot" I mean a "crest" voltage as this is what the high voltage
labs are using. Crest voltage is normally not familiar to non-engineers.
Impulse or DC voltages are not crest voltages.
At 03:19 AM 1/29/98 +0000, you wrote:
>From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
>Sent: Wednesday, January 28, 1998 2:34 PM
>To: Tesla List
>Subject: Re: Voltage/Length (fwd)
>> From: John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
>> Sent: Wednesday, January 28, 1998 12:37 AM
>> To: Tesla List
>> Subject: Re: Voltage/Length (fwd)
>> At 11:10 PM 1/27/98 +0000, you wrote:
>> >From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
>> >Sent: Tuesday, January 27, 1998 3:35 PM
>> >To: tesla-at-pupman-dot-com
>> >Subject: Re: Voltage/Length (fwd)
>> >The closest I have come is to measure single shot attached spark
>> >lengths (impulse only) as D.C. Cox has done. I have compared those
>> >with measurements from other impulse sources (Marx Banks) whose
>> >theoretical outputs can be made to match real outputs very closely
>> >in practice. The 3'/MV figure is a guide I use although I recognize
>> The 3 ft/MV at least is a number to work with. In an earlier post Cox said
>> he thought a 5 ft spark represented one million volts. My engineering text
>> says that about a 4 ft spark is one MV. But this is a one shot peak voltage.
>> I would expect that multiple sparks as with Tesla coil operation would give
>> a spark closer to 5 ft.
>> Vs = 65 x 49.8^.7 = 1000 KV
>> This equation has been used by many coilers and found to be as close as can
>> be expected to reality.
>I think you can do an awful lot better at 1MV under repetitive
>conditions. I can match that length at less than 500kV. I don't
>recall Mr Cox ever saying that "5' = 1MV" To the contrary, he has
>repeatedly stated that he has obtained around 9' under repetitive
>conditions at that voltage.
> I am now going to give an example where, despite all the careful
>measurements in the world, that notion might be subject to question.
>The cruncher: has this been tested **at different primary energies**
>(a) at the same break rate ?
>(b) at a lesser break rate to maintain an identical power throughput ?
>Let me put it like this: There are an infinite number of systems that
>may be configured to generate a MV, but each with a different primary
>energy content. i.e. - a system operating with lower Ep is obviously
>going to have a lower Ctot in the secondary system to reach that
>voltage. There is no question that can be done. The difference
>between each at a constant power throughput is voltage vs current i.e.
>if each generates 1MV, the available current must be different if
>each operates at the same frequency.
> This is what I mean by careful experiment. Nothing you have
>suggested about any experiment is exhaustive in this regard.
>> >*proven* to be real. This brings us into the realm of model validity
>> >which is outside the scope of this post.
>> Model validity is very important and must be capable of being verified by
>> calculations done correctly. This is especially important when energy,
>> power, and secondary volts are involved. This is because the Tesla coil
>> system does unfamiliar engineering magic with these variables. The JHCTES TC
>> computer program attempts to unravel the intricacies of TC design. As there
>> are no similar TC programs at present it is not possible to make comparisons
>> and changes so as to improve it.
>Model validity is tested by carefully devised experiments IMHO. I
>question this constant appeal to "magic". Either the thing is
>understandable in engineering terms or it is not. I have yet to see a
>proof that "magic" plays any part in science.
>> >What calculations? Calculations are trivial if one has a formula but
>> >having a formula is dependent on formulating for a particular piece
>> >of hardware.
>> Calculations are not trivial when done correctly. Calcs give the facts
>> rather than subjective opinions. For example the confusion that coilers have
>> over power and energy could be lessened if calculations of examples were
>Beware of garbage in, garbage out. Correct formulation is the key.
>Anyone can use a calculator.
>> >that have no basis in reality. It would appear from what people have
>> >said that Tuve et al's work is flawed and therefore useless. One can
>> How can anyone say that Tuve et al's work is flawed when they do not
>> understand the fundamentals involved? I would not say that the tests and
>> calcs of these three scientists were flawed unless I could repeat their
>> tests and calculations and show where they erred.
>They themselves admitted to experimental error. I am inclined to take
>their word for it if what they said has been reported correctly. If I
>refuted my own results which would you believe: that the results were
>good or not? I think you are going too far in saying that no-one but
>yourself understands the fundamentals.
>> >purpose. Personally, I would accept a quanitifiable error of 1% in
>> >measuring TC output voltage as being close enough to be useful in
>> >choosing between models. Jim's technique is a good one in my opinion.
>> >It gets asymptotically closer to the real answer. It will never get
>> Jim Monte's or anyone's secondary voltage tests and extrapolation have the
>> advantage that the tests can be easily verified up to 2 million volts. This
>> is the range of engineering lab high voltage tests that have been published
>> by several labs in this and other countries. The spark lengths, air
>> conditions, etc. have been carefully documented. They are all one shot and
>> not multiple sparks like with Tesla coils. Coilers have found that multiple
>> sparks are longer than one shots because of the ionization of the spark air
>> path. The Vs equation above gives spark lengths that are slightly longer
>> than the HV lab sparks for this reason.
> When you say one shot, are you talking impulse or DC? There is a
>world of difference between those modes of operation.
> I've yet to see an equation giving spark lengths for TCs that
>take break rate into account. One can argue that an equation
>giving length as a function of power does that by proxy but such
>equations as I've see ignore voltage.