Re: Big Spark Induction Coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

HI Antonio,
             I took some photos of storage scoped waveforms of a TC 
connecting to grounded object a few years ago. I'll have a poke 
around and see if I can find them. The most dramatic point about them 
was the sudden dive in secondary oscillation amplitude. I don't 
recall looking for other oscillatory artifacts. I sent on of these to 
Richard Hull about that time. I think it is available somewhere - he 
would know.

Regards,
malcolm


On 8 Jan 2002, at 18:07, Tesla list wrote:

> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
> 
> Tesla list wrote:
> > 
> > Original poster: "Kurt Schraner by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <k.schraner-at-datacomm.ch>
> 
> > Well, even in the "sim", when displaying the secondary voltage (accross
> > the sparkgap), at first, we observe a very high peak (i.e. 16kV for test
> > 24A), and then essentially low voltage accross the spark, till the high
> > f1 oscillation has ceased, when the f2 oscillation appears. This leads
> > to the second part of your posting: The tuning of the coil, including
> > primary and secondary LC's, as well as coupling, can be implemented to
> > probably optimal values, just for creating the first energy transfer
> > from prim' to sec' -and highest voltage- BEFORE secondary spark
> > breakdown. Did I get you about right?
> 
> Yes. The adjustments would depend on the spark length.
> 
> I made some experiments with an ignition coil today, and was able to
> reproduce exactly the same behaviors. When the primary circuit opens,
> the input voltage rises first, then the secondary voltage rises to
> a high value. The start of the
> spark decreases the secondary voltage to a low value, and causes a
> sudden drop in the primary voltage. After this, the f1 oscillation
> is visible in the primary, for a few ms. When it ceases, the f2 
> oscillation begins. The f1 oscillation really appears to correspond
> to the duration of the spark. I will try another experiment to
> confirm this, looking at the light from the spark.
> I noticed also another strange thing, that also appears in your
> oscilloscope images: The f1 oscillation doesn't converge to the
> supply voltage, but to a different value. The f2 oscillations
> converge to the supply voltage. I interpret the cause of this as
> a constant voltage drop at the spark being reflected to the primary,
> while a current with a significant DC component flows through the 
> secondary for some time, expending the energy stored in the coil.
> This doesn't appear in your simulations, because your "spark" is
> a linear resistor. Replace it by a voltage source and the offset
> will appear in the simulations too.
> 
> Are experimental waveforms for a Tesla coil, showing the primary
> voltage while a spark to a grounded object occurs at the secondary, 
> available somewhere? The same kind of behavior is to be expected,
> specially in a coil with a small terminal, and a short spark.
> 
> > There's just a 3rd thing, which also triggers my interest: the
> > capacitive loading of the secondary, without generating sparks. As
> > ,essentially, a "capacitive shorting" of the secondary, it produces
> > comparable first f1 ringings similar to a spark (see i.e.test 33A). But
> > it's as well forming the L2C2 resonant circuit, and as such, makes the
> > system behaving differently than with spark. The observed frequencies f1
> > and f2 concur with those fI and fII calculated from A.Bowers's idealized
> > induction coil theory, while, with a non-capacitively loaded, but
> > sparking coil, this is not generally the case. I'm yet pondering about
> > it...
> 
> My experiments show the same. It is the same double oscillation 
> characteristic of a Tesla coil, or two coupled LC tanks. As the
> coupling is high, the two frequencies are widely separated, and
> their decay time is also very different. 
> 
> > P.S. I'm afraid, Terry must stop this thread, getting too much off
> > topic?
> 
> An induction coil, besides being a classical form of power supply
> for a Tesla coil, is mathematically very similar to a Tesla coil.
> 
> Antonio Carlos M. de Queiroz
> 
> 
> 
> 
>