Re: 8 kHz Tesla Coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

> Original poster: "Kurt Schraner" <k.schraner@xxxxxxxxxxx>
> Hi Antonio, all,
> my bigger induction coil, whose secondary is wound of 0.4mm wire 
> (41.5k turns) in a stack 26 flat coils, is 60H without - and about 
> 420H with laminated iron core. See:
> http://home.datacomm.ch/k.schraner/induc_maindata.html
> However, it would support only about 150...170kV sparks (needle 
> points assumed), as a secondary voltage. The resonant frequency of 
> the cored coil is about 1200Hz (mesured), when no sparks are 
> present. From the measurements, a self capacitace of ~40pF can be 
> estimated. See:
> http://home.datacomm.ch/k.schraner/induc_analys.htm
> The smaller and newer coils (Andy's and mine) with ~26k turns of 
> 0.315mm wire in 12 "pies" have ~15H wihout and ~110H with iron core. 
> They can support around ~100...120kV.
> Think, it would be quite easy, to use those coils for low-f Tesla 
> style, but not for high power.

I underestimated a bit the inductance values. I was thinking about
an ignition coil that I have used for experiments, that has 37 H of
secondary inductance. I could make it work well as a "Tesla coil
with initial energy in the primary coil" by inserting in series
with the primary another inductor, to adjust the coupling coefficient
to the required value, and using an adequate primary capacitor.
I could then make the system operate with complete energy transfer,
oscillating at about 2 kHz. The high losses allow only operation
in the fastest modes (1:3 ou 1:7) without big differences from the
assumed lossless behavior.
A slide from a presentation here, with experimental waveforms obtained
at low power:
http://www.coe.ufrj.br/~acmq/tesla/induction.jpg
I don't remember what was the attenuation used for the output voltage.
Theoretically, it would reach 11.7 kV for each A of input current
in mode 1:3, and 7.2 kV in mode 1:7, ignoring losses.

Antonio Carlos M. de Queiroz