Re: *efficient tesla coil

 -=> Quoting Nikola Tesla Aka Chip At to Tesla List <=-

 NTAC> TAC> Message-ID: <9502161700.AA04648-at-grendel.objinc-dot-com>
 NTAC> Newsgroups: tesla.list

 >Received: from univscvm.csd.scarolina.edu by csn-dot-net with SMTP id AA28141
 NTAC> (5.65c/IDA-1.4.4 for <TESLA-at-GRENDEL.OBJINC.COM>); Thu, 16 Feb 1995
 NTAC> 09:06:06 -0700
 NTAC> Date:         Thu, 16 Feb 95 10:22:42 EST
 NTAC> Subject:      *efficient tesla coil
 NTAC> To: TESLA-at-GRENDEL.objinc-dot-com

 NTAC> Hello all,
 >enough input power is used, the BEST amount of terminal capacitance is
 >the amount that would cause ACTUAL 1/4 wave resonance in the secondary
 >winding, I.E. a coil wound with 1800 feet of wire may resonant at around
 >230 to 250 Khz.with no terminal on top, but the WIRE in the secondary
 >is a physical 1/4 wave at about 130 Khz. If a terminal is added to this
 >coil that would result is ACTUAL 1/4 wave resonance in the secondary or
 >in this case about 130 Khz, I believe at this point, ALL internal
 >capacitance of the secondary windings has been absorbed by the terminal
 >and then the secondary system can be treated in a lumped constant format.

 NTAC> This addresses a prblem that I have not been able to reconcile with
 NTAC> the calculations until now. No matter what I calculated the secondary
 NTAC> resonance to be at 1/4 wave, I always had to "halve" my primary
 NTAC> inductance to get resonance in the secondary! Now I see that the
 NTAC> calculations were correct, but that there is some property of the
 NTAC> secondary wire-length vs. resonant frequency that I am not aware of. It
 NTAC> seems like a 1/4 wave-length of wire resonates at the half-wave
 NTAC> frequency or something like that. This is without a terminal
 NTAC> capacitance, of course. Can anyone shed some light on this? And Mark,
 NTAC> thanks for this valuable info! 
 MG> The property thats not usually taken into account is that due to the
 nature of the windings inductance and capacitance, it behaves somewhat 
 like a "delay line", the wave front traveling in the secondary winding
 travels at a rate somewhat SLOWER than the speed of light, this is an
 attribute that is commonly referred to as the "Velocity factor" in
 coaxial cables. The velocity factor of air is 1.00 but the velocity factor
 of a Tesla coil secondary will be less than one depending on the
 attributes of the winding itself, as well as the form on which it is wound.
  A common misunderstanding is the quest to achive 1/4 wave resonance in the
 winding, it is a non-issue. It will be 1/4 wave resonant at only ONE fundame-
 ntal frequency, BUT THAT frequency, and the frequency that the wire would be
 resonant at streched out in a straight line, are two different things!

                             Mark Graalman


... Alias, Mark the spark
___ Blue Wave/QWK v2.12