Re: Single vs Twin TCs

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Parpp807-at-aol-dot-com>

In a message dated 12/19/01 8:46:02 PM Central Standard Time, 
tesla-at-pupman-dot-com writes:

> 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
>  
>