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*To*: tesla-at-pupman-dot-com*Subject*: RE: Vortex gap loss measurements*From*: "Daniel Boughton" <daniel_boughton-at-yahoo-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)*Date*: Sun, 03 Sep 2000 11:48:36 -0600*Delivered-To*: fixup-tesla-at-pupman-dot-com-at-fixme

Gary: Just a quick note. Tektronix has a utility on their website for converting the data files to tif files I believe. But it is free of charge. I used a similar utility on a job I was working on. Plasma too is a funny thing. It violates standard 'laws' and I suspect with the burst of current across the gap that an intense plasma is being generated which doesn't behave like a true linear resistor(which is what you already concluded). Somehow it ought to be possible to create a mathematical model of the arc resistance as a function of time which will predict behavior under specific conditions. The arc resistance would also be based on the change in current versus (t) too as you pointed out. I think you are right about the neon tubes but sign manufacturers typically rate the required transformer current by job size (primarily tube length). Nonetheless, once ignited gas plasma resistance is far less than in STP state(as you know). I worked with semiconductor etching RF generators for years and know from experience that constant ignition of the inert gas requires much less power usage than stopping and starting. Incidently these plasma chambers had a capacitive impedance and we designed automated impedance matching networks to minimize reflected power from the generator since the gas impedance fluctuated with the addition of sio2 molecules being burned off silicon wafers (The capacitance actually changed dynamically and needed constant monitoring for max power transfer). Dan --- Tesla list <tesla-at-pupman-dot-com> 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! > > >Also, does your scope generate a data file? If so, > can > >you share it? > > It does, but it's in a format native to the > Tektronix scope. I haven't > figured out how to convert it to a GIF or BMP (the > scope is borrowed from > work and doesn't have a manual). I didn't save any > of the traces since the > slope measurements were easy to make with the > cursors, but I can repeat a > subset of the measurements and just take a picture > of the screen with my > digital camera. [Crude, crude, crude!] It may take > a week or so to find > the time, but I'll post it to my web site with a > heads-up to the List when I > do. > > >Regards, > >Dan > > Regards, Gary Lau > Waltham, MA USA > > --- Tesla list <tesla-at-pupman-dot-com> wrote: > > Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com> > > > > > Today I found some time and performed a comparison > > between the gap losses of > > my single vacuum gap, and my new single vortex > gap. > > To do so, I scoped the > > primary ringdown with no secondary in place. I > used > > a Terry Fritz fiber > > optic voltage probe across the primary coil and a > > digital storage scope to > > record the results. I have not yet accurately > > calibrated the voltage > > readout, so for now, the results are just relative > > to each other. > > > > With no secondary in place, the ringdown is a > > linearly decrementing > > waveform, not logarithmic. As such, the slope of > > the ringdown indicates the > > losses in the circuit and is independent of the > gap > > firing voltage. I > > performed ringdown slope measurements at a variety > > of gap widths to vary the > > initial voltage, but the ringdown slope is a > > constant, independent of Vgap. > > > > The power to the blower motor is varied through a > > lamp dimmer and I tried > > varying the motor speed to see what effect that > had. > > At very low speed, the > > linearly decrementing waveform became slightly > > logarithmic-looking, but > > still predominantly linear. The gap breakdown > > voltage appeared to change > > slightly at low speed, but this was hard to > measure > > as it was slight and the > > bang-to-bang gap breakdown voltage is not as > > consistent as one might hope. > > > > The slope decrement figures are assuming that my > > probe is accurately > > calibrated for voltage, though I suspect it may > not > > be, so the figures are > > useful only for relative comparison purposes. > > The pressurized vortex gap decremented at > 200V/usec. > > The vacuum gap decremented at 235V/usec (17.5% > > faster). > > The vortex gap breakdown voltage is about 20% > higher > > than the vacuum gap at > > the same gap distance. > > > > Vortex gap web page: > > > > > http://people.ne.mediaone-dot-net/lau/tesla/vortexgap.htm > > > > > <http://people.ne.mediaone-dot-net/lau/tesla/vortexgap.htm> > > > > Vacuum gap web page: > > > > http://people.ne.mediaone-dot-net/lau/tesla/onegap.htm > > > > > <http://people.ne.mediaone-dot-net/lau/tesla/onegap.htm> > > > > > > Regards, Gary Lau > > Waltham, MA USA > > > __________________________________________________ Do You Yahoo!? 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