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

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

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

Hi Dave,
          Some comments on points in your post:

On 28 May 2002, at 17:33, Tesla list wrote:

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

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-
> >
> >
> 
> 
>