Re: Gap Losses

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Sunday, August 31, 1997 4:17 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Gap Losses

Hi Greg,
> From:   Greg Leyh[SMTP:lod-at-pacbell-dot-net]
> Sent:   Friday, August 29, 1997 1:47 PM
> To:     Tesla List
> Subject:    Re: Gap Losses
> Malcolm Watts wrote:
> > Actually, within your post there lies the nub of the problem I think....
> > 
> > > > > Well, I know that 5.3 ohms is too low for a 4-gap rotary, and I suspect
> > > > > that 50 ohms is pushing the high side for most gap systems, even the ones
> > > > > with a zillion static gaps in series.  My rule of thumb at this time is:
> > > > >
> > > > > Zchar = 4 ohms X number of series gaps in primary switch.
> > > > > -GL
> > > Upon further thought, I realized that my above rule of thumb would only be
> > > optimal within a fixed range of primary currents, say 2500 to 3000A.  As the
> > > primary current is reduced, the gap resistance goes up.  This increase in
> > > resistance at lower operating currents would necessitate an increase in Zp,
> > > in order to preserve the primary Q.  So 100 ohms might be OK after all.
> > > What was your reasoning for choosing 100 ohms?
> > > -GL
> > 
> > In fact, increasing Z surge decreases Ip which increases Rgap and
> > also Vgap (conducting) to some extent. I suspect that what you have
> > hit is the product of lowest Vgap and Igap.
> If we knew the curve that relates Rgap to Igap for a single spark gap,
> then it's just a little bit of differential calculus to determine Vpri
> and Zchar at the local efficiency maxima (there might be more than one 
> solution since the curve that relates Rgap to Igap is non-linear).

 I would say that would be a measurement well worth taking. Given f 
for a particular secondary, it would be nice to be able design the 
primary and nominate Vp to suit the number of gaps required (which 
I've found is dependent on the charging current vs cap size). Then 
again, I suppose one has to make do with transformer/s on hand and 
there is a requirement to get an ideal V/I mix in the resonator for 
best sparks. Love to know what that is.
    Some of the recent thinks: There may well be a quanitifiable 
reason why low-f systems do produce better sparks. I looked at 
oscillograms of the minicoils under optimal inload conditions and 
noticed that it took several cycles of ring before the rings dropped 
abruptly. I am thinking that in a low-f system, the oscillation might 
be low enough to feed the spark directly. There seems to be a degree 
of sluggishness about establishing an attached streamer.