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Voltage/Length (fwd)
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From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Sunday, February 01, 1998 4:35 PM
To: Tesla List
Subject: Re: Voltage/Length (fwd)
John,
Unfortunately, one must take all factors into account in this
mwtter:
> 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.
Unfortunately not (see below).
> 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.
Whether it appears to cloud the issue or not, it is a simple matter
to demonstrate that spark length is far more dependent on break rate
than voltage in a TC. In fact average throughput is probably as
significant a factor in this as repetitively heating the air. In many
ways, it amounts to the same thing. Greg has given a set of figures
ranging from several feet to a peak recorded length of around 30 feet
for *a single voltage*. Difference? The break rate from 1 to 240 odd
BPS. I am even going so far as to assume the primary cap reached the
same voltage at extremes of break rate. One might expect it to fall
off at the higher break rate under some conditions.
One of my coils: BPS = 1 ( Vout est around 300kV ), attached
length = 12". BPS = 3 - 4, attached length = 22". That was with
exactly the same gap setting etc.
Show me a coil whose repetitive length comes close to or matches
the single shot length and I will show you a coil fit for the garbage
can. That is an exact description of my first one.
> 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
> statements.
Abstract perhaps? Well, there are a couple of real examples above.
Formulae that do not take all factors into account are useless, even
when calculated to the 100th decimal place.
> 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.
Alright, let's call it "peak" then. The highest the system produces
at the time the measurement is being made. Impulse vs a slowly ramping
DC source gives less time for leaders to form.
An interesting exercise is to calculate voltage for a
lightning stroke that is distance dependent, and then to discover to
one's horror that one is out by an order of magnitude if the figure
given by lightning researchers is even moderately close to reality.
> John Couture
Malcolm