RE: Static Gap question.

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

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
 >    >
 >    >
 >    >
 >
 >
 >