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RE: Does a "regulating" coil really waste energy?
Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
On 29 May 2002, at 11:40, Tesla list wrote:
> Original poster: "Dave Larkin by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> 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
OK, so we're talking several transfers - a typical situation for air-
streamers, not connected ones.
> You are correct that the 'notch' time is determined mostly by k, which
> surely also determines the operating primary Q to a large extent?
I guess it's semantics - I prefer to consider the primary divorced
from its "losses" to the secondary. Since k sets the rate of primary
loss in this situation, there is nothing you can do about it other
than lower k (which then boosts gap losses). I don't really consider
"losses" to the secondary as losses per se since the energy largely
remains in the system (no streamers). Under those conditions, most of
it is eventually lost in the primary gap as multiple transfers
At least by considering the primary and its gap in isolation, you
can see where improvements to that part of the circuit can be made.
> > > While textbook Q formulae for LCR resonance predict quite high primary
> > > 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,
> > > fact the only way to increase Qpri for a given value of Qsec is to
> > > k, which is exactly what adding an off axis inductance does! (This does
> > > mean we should all add massive off axis inductors, the penalty in
> > > 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!
It certainly dips as streamers form but for air streamers still
remains quite high as evidenced by the multiple pri-sec transfers
which continue (if allowed to by a lack of major quenching efforts)
under those conditions. I don't have tabulated data and obviously the
loaded Q for air streamers varies somewhat but captured scope
waveforms suggest a dip of 50 - 70% or so on unloaded pre-breakout Q.
For attached output sparks, loaded secondary Q drops into the dirt.