RE: Practical limit to number of turns on primary ? ? ?

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

Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>



Thanks for the response.  But what if we could pull the primary capacitor
out of the equations.
If we set the primary source and capacitor as a constant and assumed we had
a secondary which we could vary the resonant
frequency without really changing its load or coupling characteristics.  How
would number of turns on the primary affect
efficiency in that case???  I think the two important parameters here are
series impedance losses and the coupling between
a relatively small diameter primary and relatively large diameter primary.


Dan -

The limit to the number of primary turns is dependent on the primary
capacitor. This capacitor is an energy storing device and must be able to
store the proper amount of energy required for efficient operation of the
primary coil. This means the capacitor must meet several conditions, the
tuning requirement, the energy requirement, etc. You have to solve several
equations simultaneously. This is why engineering handbooks say "The design
of Tesla coils is empirical".

Start with the energy requirement -

       Cp = J/V^2    Assumes 50% efficiency

      J = Joules per bang
      V = Power supply secondary voltage

The tuning requirement is   LpCp = LsCs

Note that as you change the joules the Cp changes, the primary turns
changes, the efficiency changes, etc. There are other parameters and
equations involved. In general as the Cp is made smaller the primary turns
increase, and the efficiency decreases. A very small Cp gives you many
primary turns at very low efficiency. The trick is to find the optimum
operating parameters. Solving this problem with an NST only enhances the
challenge.

Your question in many forms has been asked many times in the past on the
List. The answers are always interesting.

John Couture

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-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, January 27, 2003 1:29 AM
To: tesla-at-pupman-dot-com
Subject: Re: Practical limit to number of turns on primary ? ? ?


Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<dhmccauley-at-spacecatlighting-dot-com>

Thanks for the replies, however they do not answer my question.  I am
already aware about the resonant relations between primary and secondary
etc...
My question, was what is the practical limit for size of the primary in
relation to the secondary coil.  This isn't a tuning question.  Its one of
efficiency and performance vs.
primary number of turns.  Of course this efficiency and performance vs.
primary number of turns would assume constant primary conductor size and
spacing.

Thanks

Dan