Re: Lower secondary cself => better performance?

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Duncan,

On 15 Feb 01, at 18:10, Tesla list wrote:

> Original poster: "Dr. Duncan Cadd by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
> 
> Hi Malcolm, All!
> 
> >Original poster: "Malcolm Watts by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>
> >
> 
> 
> <snip - good stuff BTW!>
> 
> >You can typically do a lot better - I have seen transfer efficiency
> >for a single pri-sec energy transfer approaching 90% on a small coil.
> >Whether that figure is degraded then depends on whether the secondary
> >dumps its load in an (attached) output discharge at that moment ro
> >whether pri-sec transfers continue which is the case for air
> >streamers.
> 
> 
> Now that I would never have expected!  You mean including
> quenching/gap losses?  That's amazing.  But for a small coil, hmmm.

Same applies to large coils according to scope waveforms. But ideal 
transformers are lossless and the TC is just a transformer whose 
worst losses happen to reside in the primary and more specifically, 
the gap discharge if good quality conductors are used. Otherwise, 
it's pretty much reactive.
 
> Nice to have your thoughts re changing one thing at a time.  Learned
> that one the hard way in quite a few chemistry labs!  The problem of
> course is that isolating the variables is often less than
> straightforward.  I'm also curious as to why the quenching should have
> become significantly harder with the increase in Ctop and Lp.  Could
> it be that the energy is exchanged for a few more cycles between
> primary and secondary before the surface gradient reaches breakdown
> value, i.e. driving a larger load it ramps up more slowly?  That's
> given me something to think about.

How quickly it rings up is a function of Fr and k. Lower Fr and/or k 
= more time taken for a single transfer.  
      
       I am being very wary in talking about quench and specifically 
mentioned power arcs. I've found it's impossible to achieve a first 
notch quench if the secondary is not allowed to break out *and 
attach* without incurring serious gap losses. There is more than one 
note from myself referring to this in the archives from a year or two 
back, probably with quenching mentioned in the subject line. Power 
arcing is something that can be controlled more easily though. I'm 
not sure exactly why it was a bugbear in this case but the primary 
losses were considerably lowered as I added around 50% more Lp in the 
case referred to. Something about the altered primary dynamics has to 
be the culprit. I can't see why the topload should have mattered.

      An expt worth doing for anyone who believes you can achieve 
ideal gap quench: try it without allowing breakout and monitor the 
results on the scope to make sure you've done it. I had to go to 
extraordinary lengths to force my coil to do this. I ended up with 
the primary gap discharge being blown into a (circular type) arc 
several inches long. Compare your output to a grounded rod with and 
without implementing these measures. I'd love to hear how others have 
done it (if they have) and not lost any more power. 

Regards,
malcolm