Re: Fwd: Re: Calculating streamer breakout of top-loads

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

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

Hi Gerry,

On 9 Sep 2003, at 8:05, Tesla list wrote:

 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >
 >
 > >X-Envelope-From: gerryreynolds-at-earthlink-dot-net  Mon Sep  8 19:01:21 2003
 > >From: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 > >To: "Tesla list" <tesla-at-pupman-dot-com>
 > >Subject: Re: Calculating streamer breakout of top-loads
 > >Date: Mon, 8 Sep 2003 19:00:22 -0600
 > >X-Mailer: Microsoft Outlook Express 6.00.2800.1158
 > >X-DCC-SdV-Metrics: dick.jymis-dot-com 1179; Body=1 Fuz1=1 Fuz2=1
 > >
 > >Malcolm,
 > >
 > >This would be my prefered way of characterizing the primary/secondary coil
 > >system also.  Spark length prediction based on delivered power (watts) thru
 > >the spark gap would, to me, be more reliable and be a better predictor of
 > >ones design.  Sorta decouples the charging system design from the coil
 > >design (or at least maybe to some extent).  Please tell me what the John
 > >Freau equation is based on (SG power in watts or xformer input in VA)

Wallplug draw. The fact that operating results often don't match the
theoretical result probably says something about the electrical coil
parameters as well as the power supplies used. The basic recipe for a
given (input) power level appears to be:

- highest possible output voltage from the coil to give reach and
induce streamers from far objects (implies high energy shots which
for a given power level translates into low breakrate)

- very high output current implying a high capacitance in the
secondary system (a conflicting requirement with the the first point)

- high enough breakrate to promote streamer growth while not
restricting it through having such a high degree of ionization as to
clamp output voltage excessively (conflicts with requirement 1 again)

The question is, where does the balance lie? There appears to be
little doubt that there is an broadly-defined inflection on the
breakrate curve as breakrate is reduced. from past experience I
suspect that the dependency on input power is minimal. That leaves
the V/I ratio in the secondary to be explored. My tabletop design
(yet to be fired) aims for a reasonably high capacitance in the
secondary system, yet not so high as to reduce output voltage too
much (don't ask me to quantify what I mean by "too much" - I have the
figures on the back of an envelope at home somewhere). The breakrate
will be about 100 (2 Fmains for me) and I will use as large a primary
capacitor as I can get away with while still having the primary gap
fire reliably at about peak transformer output voltage. For my
transformer (5kV, 30mA) I remember calculating a figure somewhere
around 0.7 (0.9?) Joules. Finally, minimizing gap losses are all-
important. You can probably guess how I've gone about doing that.

Malcolm