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Re: Notes on Terry's observations
Hi Terry, Antonio,
> Hi,
>
> big snip....
>
> >If the coil is designed to operate with already some loss due
> >to skin effect and other losses that increase with frequency at
> >the resonance frequency with a large top load, the other resonances
> >will be at much higher frequency, and so will be heavily damped,
> >as you correctly point out.
> >About "racing sparks", I still believe that the reason is simply
> >the accumulation of static charges in the surface of the resonator.
> >
> >Antonio Carlos M. de Queiroz
> >
>
> The graph at:
>
> http://users.better-dot-org/tfritz/Current.jpg
>
> Shows the current draw of the coil generally increasing as frequency is
> increased. I think this is due to the increasing losses in the coil.
>
> It is interesting to note that at about 110.01kHz the current drops to
> almost zero (660nA) (I notice that I now us the term "about" for 5 digit
> numbers ;-). The graph takes data at every 10kHz so it missed the true
> level of the peak before at 84.63kHz. It was 1.07mA About a 1:1600 ratio.
> The input voltage is 0.707 Vrms. The resistance at the peak is 660 ohms
> while the low current point had a resistance of 1.07M ohm. The wire on the
> coil is 2690 feet long. That gives a 1/4 wave frequency of 91410 Hz. I
> could not find any correlation between the frequency and anything I
> measured but I don't think that is a surprise. However, I did try...
>
> IMHO, I think racing arcs are caused by pure transformer action as the
> secondary coil is suddenly hit by the first impulse from the primary. A 15
> turn primary mixed with the lower say 300 turns of the secondary gives a
> voltage transformation ratio of 20. So the 20kV on the primary gets
> transformed to 400kV before the resonant action can start. Raising the
> secondary lowers the coupling and reduces the initial induced voltages so
> the arcs can be stopped by moving the coils away from each other. I have
> not spent a great deal of time thinking about that, so perhaps I am wrong
> there??
>
> Cheers,
>
> Terry
Sorry for including all the text but it puts my comment in context.
Without any substantial proof I am inclined to the overvolt/unit length
theory for a couple of reasons: I can demonstrate that racing
sparks never occur on one of my coils which always accumulates a
subtantial amount of "substrate" static in dry weather, and secondly,
I can create racing sparks on any coil I like by simply running at a
high enough energy - *in single shot mode*. No coil I have tested
accumulates subtantial buried charge in this mode.
Regards,
Malcolm
P.S. I am following the V/I distribution thread with considerable
interest.