Re: Big Spark Induction Coil

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Antonio,

At 09:27 PM 1/8/2002 -0200, you wrote:
>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 is a simulation of a coil having the secondary shorted at:

http://hot-streamer-dot-com/temp/arc1.gif

Cheers,

	Terry