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Re: This phase shift stuff...

Hi Bryan,

	The current from the top to the bottom of the secondary does vary, as a
delayed cosine wave.  The current is absorbed by the self capacitance of
the coil.  The current is literally sucked out of the secondary along its
length into charging to region around the coil to a given potential.  The
current is max at the base and is then reduced along the length to some
value.  In the "no top terminal" case, this top current value approaches
but never reaches zero.  There is a lot of area at the top of a bare
secondary that needs charging and the last top winding performs this
function.  This is why people that have series LEDs in a test coil still
see current in even the last winding.  Electrostatic field maps of the top
of the coil show the high potential stresses that charge the area around
the top of the coil and the current it takes to do this charging.  However,
phase shift is NOT a necessary condition in this case and thus the question.

	However, as you and Antonio suggest, a long thin secondary with no top
terminal should be the most likely to show phase shifting.  This approaches
a classic delay line.  So, if I will find phase shift, that should be the
case where I will be most likely to find it.  If I don't see it there, I
think the phase shift will simply not be a factor.  If I do, then there is
the question of how to control this factor to the best advantage or if it
even can help contribute to longer sparks.  

	Of course, we almost all use top terminals.  However, this is still a good
test since it is an extreme.  If I don't see phase shift in this case, I
will certainly never see it in a coil with a terminal.

Thanks for the great input!


The science goes on...

	Terry
 


 

At 11:51 AM 2/17/99 -0500, you wrote:
>Terry,
>
>Even in concept, I think you are right Terry, considering the current
variation
>between the top and bottom of a coil can only be significant without a
toroid. The
>toroid opens the top of the coil and the current is virtually identical
between top
>and bottom. The only remaining source of variation can be the interwinding
>capacitance and self indiuctance which are both minute effects (if I have
been
>following the threads correctly) The effect of the toroid swamps any phase
variation.
>
>Any dissenting opinion? Please feel free to tell me that I am FOS (Full of
>supposition)  if you think so. I have no ego tied to this, enlighten me.
>
>Bryan Kaufman
>
>
>Tesla List wrote:
>
>> Original Poster: Terry Fritz <twf-at-verinet-dot-com>
>>
>> Hi All,
>>
>>         As we all know, I like the theory that there is very little
phase shift in
>> voltage and/or current from the top to the bottom of the secondary coil in
>> Tesla coils.
>>
>>         Malcolm got me started... :-))
>>
>>         So here's the question...
>>
>>         Does anybody have a Tesla coil system or REAL setup that has
SIGNIFICANT
>> PHASE SHIFT from the top to the bottom in the secondary?  I have, what I
>> think, is the best equipment in the world to measure such things.
>> Everything I have measured, so far, points definitely to the lumped
>> parameter model...
>>
>>         Now, I am looking for the exception…  to prove me wrong...
>>
>>         So what kind of REAL Tesla coil system can I put together that
will show
>> all that phase shift, 1/4 wave, and transmission line effect stuff?
>> Perhaps, it is a forgone conclusion that the secondary voltages and
>> currents are pretty much in phase within a Tesla coil (there really is a
>> "little" shifting).  However, if anyone has a major exception, I have the
>> resources ready to pour into reproducing and studying this exception.  It
>> is time to put this matter to rest once and for all...
>>
>> Go ahead…  MAKE MY DAY! :-)))
>>
>>         Terry
>
>
>
>
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