Re: Tesla turns ratio ?

Subject:  Re: Tesla turns ratio ?
  Date:   Wed, 11 Jun 1997 17:00:15 +0500
  From:   "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
    To:   Tesla List <tesla-at-pupman-dot-com>

On Tue, 10 Jun 1997 23:37:37 -0400 Owen Lawrence
<owen-at-iosphere-dot-net> wrote;

> > Why people care about the number turns is beyond me since a Tesla 
> > coil dosen't operate on a turns ratio!

> Alfred, can you please elucidate?  I thought the number of turns has a
> direct effect on the inductance of a coil, a very important Tesla
> parameter.  Or are you just talking about primary/secondary turns ratio? 
> Thanks.
Owen, you are correct when you say the number of turns effect the 
inductance of a coil and as such one should strive to get as any 
turns on the secondary as is practical. BUT the actual turn count is 
irrelevant because the ratio of transformation in a Tesla coil IS NOT
related to the ratio of primary to secondary turns! For the benefit 
of anyone who is not familiar with the derevation of the ratio of 
trasformation in a Tesla coil here it is:

              E = .5 x C x V^2  :energy stored in a capacitor
         Eprimary = Esecondary  :conservation of energy law

combining the two equations gives;

  .5 x Cprimary x Vprimary^2 = .5 x Csecondary x Vsecondary^2

dividing both sides by .5 gives;

       Cprimary x Vprimary^2 = Csecondary x Vsecondary^2

Solving in terms of Vsecondary gives;

                  Vsecondary = SQRT (Cprimary / Csecondary)

Since at resonance the capacitive reactance is equal to the inductive 
reactance but they are oposite in nature, it can also be expressed 

                  Vsecondary = SQRT (Isecondary / Iprimary)

where I is inducatance

Realize this is a theoretical maximum and many factors effect it such
as resistive losses, dialectric losses, coronal leakage, ect. 
Examining the above equations should clearly show that ones goals are 
to make the secondary capacitance as small as possible while at the 
same time making the secondary inductance as large as possible or 
looking at the primary circuit you want to make the primary 
capacitance as large as is practical and the primary inductance as 
small as is practical. I say practical because a one turn wide 
diaeter primary may give minimum inductance but it may not transfer 
all the primary energy to the secondary and using too large a primary 
capacitance is no good because the power supply won't be able to 
fully charge it during any given half cycle.


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