Re: Gap Losses

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).