Re: Gap Losses

From: 	Greg Leyh[SMTP:lod-at-pacbell-dot-net]
Sent: 	Wednesday, August 27, 1997 1:19 PM
To: 	Tesla List
Subject: 	Re: Gap Losses

Malcolm Watts wrote:

>             Greg asked....

> > 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.
> >
> > I would be interested to know where yours (and others) Zchar values fall,
> > for your favorite 2-coil systems.
> > -GL
> My mini coils with the first transfer loss reported had Zp on the
> order of 50 Ohms. I am shooting for 100 Ohms in a new design I have
> been commissioned to build for display purposes.

Congrats on the commissioned piece!  Your client should count his lucky stars
for finding a world-class Tesla coil expert so close to home!

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?