RE: Does a "regulating" coil really waste energy?

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

Original poster: "Dave Larkin by way of Terry Fritz <twftesla-at-qwest-dot-net>" <teslaman15-at-hotmail-dot-com>

Hi Malcolm

> > >Please correct me if I'm mistaken - I thought that the secondary Q was
> > >unimportant since streamer "losses" drive the Q into the dirt, but that
> > >maximizing primary Q was still desirable?
> >
> > I am unsure to which part of my post your comment alludes to, however...
> >
> > In a TC the primary's job is basically to dump as much of its energy as
> > possible into the secondary asap, in a typical well quenched system this
> > happens in 10-30 rf cycles.  This implies a low Q!
>
>Actually, the number of cycles it takes to effect a one-way energy
>transfer is determined mostly by k and is typically 3-4 cycles for
>most systems.

I found that, both by measurement and simulation, the time to quench is 
around 10-30 cycles. (anything the far side of 20 indicates either a very 
low k or terrible quench!).  If one takes the peak of the first 'notch' as 
the point of total energy transfer, then it would come out in the range you 
suggest.

You are correct that the 'notch' time is determined mostly by k, which 
surely also determines the operating primary Q to a large extent?

> > While textbook Q formulae for LCR resonance predict quite high primary 
>Qs
> > based on the L, C and approximate R, these neglect the Zsec, transformed
> > back down to the primary.  The (relatively) low Qsec implies a low Qpri, 
>in
> > fact the only way to increase Qpri for a given value of Qsec is to 
>decrease
> > k, which is exactly what adding an off axis inductance does! (This does 
>not
> > mean we should all add massive off axis inductors, the penalty in 
>increased
> > spark gap losses, set against the dubious benefits of increased Qpri,
> > doesn't look good)
>
>
>Secondary unloaded (pre-spark) Q's are more than an order of
>magnitude higher than those of the primary (the main dampener there
>being the gap). However, most primaries even without the gap would be
>struggling to achieve an unloaded Q of several hundred.
>

By 'quite high' I meant high relative to the operating primary Q, which a 
few hundred certainly qualifies as!  Something I would be interested in data 
on is the effect of the 'ion cloud' on secondary pre spark Qs.  While for 
the first firing the secondary Q is probably quite high pre spark, one would 
expect the Q to take a dive in the subsequent cycles, as the breakout 
voltage dips to almost nothing.  My experimental setups have never been able 
to prove/disprove this, owing to 1950s vintage test equipment!

-Dave-

>Regards,
>malcolm
>
> > I believe, the logic behind Greg Leyh's real time tuning attempt was to
> > allow re-tuning on load, to compensate for the 'ion cloud' and streamer
> > capacitance effects.  The relatively low system Q means that this had
> > little/no effect (correct me if I'm wrong Greg).
> >
> > -Dave-
> >
> > >
> > >Gary Lau
> > >MA, USA
> > >
> > >  -----Original Message-----
> > >From: 	Tesla list [mailto:tesla-at-pupman-dot-com]
> > >Sent:	Tuesday, May 28, 2002 10:08 AM
> > >To:	tesla-at-pupman-dot-com
> > >Subject:	Re: Does a "regulating" coil really waste energy?
> > >
> > >Original poster: "Dave Larkin by way of Terry Fritz 
><twftesla-at-qwest-dot-net>"
> > ><teslaman15-at-hotmail-dot-com>
> > >
> > >You are quite right.  The myth that off axis inductance directly 
>'wastes'
> > >energy is a hangover from the old days.  All it does is reduce k a 
>little,
> > >which may lead to slightly increased spark gap losses beacuse of the 
>longer
> > >'notches'.
> > >
> > >More generally on the subject of real time tuning - Greg Leyh used a
> > >monster
> > >litz wire tuner on his big coil, and quite a few others have tried 
>other
> > >schemes since, no-one has reported any amazing benefits.
> > >The Tesla coil is actually a fairly low Q device (under sparking
> > >conditions), so these small alterations seem to make little difference.
> > >
> > >-Dave-
> > >
>