RE: Vortex gap loss measurements

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

hi Gary,

On 2 Sep 00, at 20:02, Tesla list wrote:

> Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com> 
> 
> Hi Dan:
> 
> Comments interspersed:
> 
> >Original poster: "Daniel Boughton" <daniel_boughton-at-yahoo-dot-com> 
> >
> >Gary:
> >
> >This is a very interesting experiment. First, when you
> >measured the slope during the ring down, did you see
> >the same size decrement of each succesive oscillation?
> >Is this what you mean by linear as oppossed to
> >logarithmic? 
> 
> Yes, the envelope of the ringdown is precisely triangular.  You can line up
> a straight edge on the ramp and it follows the envelope exactly, right down
> to zero.
> 
> >Traditional wisdom purports that the
> >decay is according to V(t)=V(i)e^-rt where V(i) is the
> >forced initial potential on the capacitor. Your
> >results are very interesting however in that it flies
> >in the face of convention. The derived equation must
> >be something like V(t)= V(i)*-krt. 
> 
> I think the thing wrong with the traditional equation is that it assumes a
> constant arc resistance.  I'm guessing that the arc resistance is a function
> of arc current, and not a constant.
> 
> >I wonder if without
> >the secondary it is linear due to resistive losses
> >only. Without the secondary the additional absorption
> >of energy via the secondary mutual inductance is
> >missing which accounts for the linear decay? 
> 
> I think all of the losses have to be resistive, it's just a question of
> whether it's a constant resistance.
> 
> >Also what
> >I found interseting was that with the gap distance the
> >slope remained constant. I would have expected greater
> >gap resistance at further distances but it seems that
> >the plasma provides a constant resistance no matter
> >how wide the spark gap is set (within reason of
> >course-I 'm sure at a foot the resistance would be
> >substantial as compared to 300 mil).
> 
> Yes indeed!  I also expected the losses to be proportional to arc length.
> But with a wider gap, the breakdown voltage is higher with proportionately
> higher tank currents, and if my belief that arc resistance diminishes with
> higher currents, it may all be a wash.
> 
> Here's a thought experiment.  I don't know the answer, perhaps someone else
> does.  If one has a 3 foot long neon sign tube and a 6 foot neon sign tube,
> the longer one will obviously require a higher voltage to start ionization.
> But once started, won't they both draw the same current from the same NST?
> If so, this suggests that gap arc resistance is strictly a function of gap
> current, not distance.  If not, then I give up!

I have metered a Jacob's ladder to watch the effects of arc 
length and it showed voltage climbing as the spark rose. The 
current hardly varied. The changes in arc length were pretty 
significant and the voltage would have roughly doubled for a 
change of around 10 in arc length. Agree with all your other 
conclusions.

Regards,
malcolm