Re: Gap Losses
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Thursday, August 28, 1997 4:44 PM
Subject: Re: Gap Losses
Actually, within your post there lies the nub of the
problem I think....
> 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?
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.