Re: Single vs Twin TCs

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Steve,

Your suspicion is most likely correct. There's no indication that a twin
transfers energy from primaries to the secondaries with any greater
efficiency than a single TC. One could make a hand waving argument that,
for a symmetrically balanced twin, half of the available power goes into
each secondary. Empirical evidence seems to suggest that spark length is
proportional to the square root of input power. So, let's assume that a
single coil TC outputs a streamer length "X" for a given input power
level. If we now apply the same power into a bipolar twin, it should be
distributed equally between the twin resonators. This implies that the
estimated spark length for EACH secondary would be about 0.707*X. The
combination should be a resonator-to-resonator spark length of 1.414*X
for the same input power. While the above description gives us a
numerical answer, it doesn't really tell us much about the physics of
WHY this occurs. So let's briefly talk about why this may be occurring
at a more fundamental level...

In a bipolar twin, the outputs are 180 degrees out of phase, and the
E-fields between the two toroids will tend to aid each other.
Conservation of energy implies that the output voltage of each secondary
will be about 0.707 times that of a the single TC case when driven by
the same bang size. Now suppose we initially position the toroids of the
twin coils such that they are separated by distance "X" (above). Because
of the out of phase condition, the voltage stress (and resulting
E-field) in the gap between the toroids will be 1.41 times greater than
the e-field between coil TC placed a distance "X" from a grounded wall.
Streamers propagate only when the local e-field at streamer tips exceed
the breakdown voltage of the surrounding air. Because of the enhanced
e-field between the toroids of a twin, the e-fields at the tips of the
streamers are enhanced, causing them to propagate further than if they
were heading to ground. This is probably clear as mud, but it's the best
I can do for now... :^)

BTW, thanks for the recent set of measurements. I believe that a
resonant charging DC system combined with a variable triggerable spark
gap offers the best vehicle for doing spark length and behavior studies
versus bang size and break rate.

Best regards,

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com


Tesla list wrote:
> 
> Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>
> 
> Hi list,
> 
> A twin TC is alleged to be more efficient than a single TC.  That is, for
> the same power, a twin allegedly can develop a longer streamer between the
> toroids than a single coil can to the air or ground.  Can someone explain
> exactly why?  Is it more than the idea that two smaller diameter primaries
> might transfer energy more efficiently to the secondaries than one larger
> primary to one secondary?  I suspect the explanation is more related to what
> is going on in the air between the toroids.  Your thoughts?
> 
> --Steve