RE: Static Gap question.

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

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

Definitely NOT mains-resonant.  A 15/60 NST at 60 Hz is resonant with just 
over 10nF, and I had a 20nF cap.  It's worth pointing out that there was no 
secondary present, so all of the energy was being burned in the gap, which 
may help explain the tendency to rapid refirings (if there's a lot of hot 
ions floating about in the gap).

Regards, Gary

.

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz>

Hi Gary,
           I agree with all you have to say on the static gap below.
Looking at the waveforms on your website, I am guessing that the
charging system may not have been accurately mains-resonant. T-F ?

Malcolm

On 12 Feb 2004, at 8:11, Tesla list wrote:

  > Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
  >
  > I know of no mechanism or previous reference to a gap's on-resistance
  > being related to its area.  I think the benefits to a large area are:
  > 1) electrode erosion is minimized if it occurs over a large area 2)
  > localized heating at the point of discharge is minimized if it occurs
  > over a large area 3) ionized air is more easily blown away if the
  > discharge area is large, leading to a more consistent breakdown
  > voltage
  >
  > Remember that the cross sectional area of the gap arc (arc resistance)
  > is determined by the gap current, not the electrode geometry.  When
  > you have a gap between two cylinders, it only occurs at one point
  > (more or less) at any given instant.  Why it doesn't tend to favor the
  > ends with sharper features or linger at some arbitrary site where
  > ionized gasses and temperatures are more favorable to breakdown is a
  > mystery to me.
  >
  >  >From another of your (Luke) posts, you ask about the consequences of
  >
  > rather small gap distance adjustments.  Don't get hung up on this.
  > Static gap breakdown voltage is not as predictable as any Tesla design
  > programs, tables, or formulas may lead you to believe.  None of these
  > predictors takes into account the very recent history of the gap -
  > i.e. how recently it has fired, which affects air temperature and
  > ionization levels.  Look at this actual scope waveform taken on a
  > static gap: http://www.laushaus-dot-com/tesla/measured_waveforms.htm.
  > Notice how much variation, both time and voltage,  there is from bang
  > to bang (the rapid vertical traces).
  >
  > It is imperative to understand and believe that a static gap will
  > never (except for 5 seconds on the 5th Sunday of each month) fire at
  > the peak voltage of each mains half-cycle 120 times per second.
  >
  > Gary Lau
  > MA, USA
  >
  > .
  >
  > Original poster: robert & june heidlebaugh
  > <rheidlebaugh-at-desertgate-dot-com>
  >
  >
  > Luke: Yes the large area has two advantages; The total resistance of a
  > large area gap greatly reduces gap resistance. When mounted vertical
  > the gap is self cooling. When the small space of the series gap fires
  > the total gap spacing drops to minimum by the ion cloud conduction
  > within the large pipe area dropping the total capacitor charge to a
  > low voltage delivering a large ammount of total capacitor discharge
  > power to the primary coil.  In contrast the safety gap dampens over
  > voltage but dose not discharge the capacitor charge acting like a
  > voltage limitor not a spark gap. The same basic service but totaly
  > different results.
  >               I use plate discharge spark gap discharge in my gas
  >               lasers.
  > The
  > large space involved produces another action not noticed on small
  > spark gaps. That is a traveling wave action. I start  the discharge at
  > one end of the laser and the arc travels the length of the tube with
  > the light to compound the intensity at the output end of the laser.
  > THIS DELAY LINE TRAVELING WAVE IS NOT SEEN ON TC SPARK GAPS, Because
  > they are not 1 meter long and the capacitors are not strip line
  > capacitors.
  >       Robert   H
  > --
  >
  >
  >    > From: "Tesla list" <tesla-at-pupman-dot-com>
  >    > Date: Wed, 11 Feb 2004 08:03:37 -0700
  >    > To: tesla-at-pupman-dot-com
  >    > Subject: Static Gap question.
  >    > Resent-From: tesla-at-pupman-dot-com
  >    > Resent-Date: Wed, 11 Feb 2004 08:13:25 -0700
  >    >
  >    > Original poster: "Luke" <Bluu-at-cox-dot-net>
  >    >
  >    > I have looked around at the types of static gaps and have a
  >    couple
  > thoughts
  >    > of my own.
  >    > But let me see if I get this right.
  >    >
  >    > Assumptions.
  >    > The versions using the copper pipes in parallel to on another
  >    work
  > well
  >    > because they allow lots of surface area for the gap to cool thus
  > quenching
  >    > it rapidly?
  >    >
  >    > Gaps like the hyperbaric do not use the large surface area but
  >    the
  > good
  >    > quenching is assisted by the high volume of air?
  >    >
  >    >
  >    > Question 1.
  >    > If the gap is cooled off sufficiently and the gap is quenched
  >    well
  > say by
  >    > large amounts of air is there any other benefit to using a larger
  > surface
  >    > area for the spark gap?
  >    >
  >    > And question 2.
  >    > The JavaTC program estimation of the arc distance in relation to
  > potential
  >    > is based on the surfaces of the spark gap being curved like as in
  > large
  >    > dia. balls or pipes in parallel.
  >    > This assumes the distance between electrodes is not greater than
  >    the > diameter of the electrodes. > > Would the same approximate
  >    distances be obtained for said voltage if
  > flat
  >    > electrodes were used parallel to one another?  Say like two 1"
  >    dia.
  > discs
  >    > separated by ½".  Would that have a breakdown voltage close to
  >    the > breakdown voltage of two 1" dia. copper pipes in parallel to
  >    one
  > another?
  >    >
  >    >
  >    > Thanx
  >    >
  >    > Luke Galyan
  >    > Bluu-at-cox-dot-net
  >    >
  >    >
  >    >
  >
  >
  >