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Re: again!!

Hi Mark,

At 07:43 PM 12/1/98 -0800, you wrote:
>hello all!
>..........does anyone know the formula for the inductance of a cone 
>shaped primary?...



Here is an excellent post by Bert Hickman.  This post was found by
searching for "conical primary inductance" in the archives at the list's
web sight at:  www.pupman-dot-com  .

=============================================================================

     To: "'Tesla List'" <tesla-at-pupman-dot-com> 
     Subject: "Slinky" Primary / Sloped Archimedes Spiral Primary Equation 
     From: Tesla List <tesla-at-stic-dot-net> 
     Date: Fri, 14 Aug 1998 23:38:53 -0500 
     Approved: tesla-at-stic-dot-net 




----------
From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Friday, August 14, 1998 12:06 AM
To:  Tesla List
Subject:  Re: "Slinky" Primary / Sloped Archimedes Spiral Primary Equation

snip...........

Hope this is what you're looking for. Included are Archimedes, helical,
and inverse conical primaries. The helical and Archimedes forms are from
Wheeler, and the inverse conical is a hybrid form that appropriately
weights the vertical and horizontal components of Helical and Archimedes
inductances. 

All dimensions are in inches, and L is in microHenries. While the
Inverse Conical calculation is a little "hairier" than the first two,
it's relatively easy to calculate for any desired angle, especially if
set up in a spreadsheet. 
------------------------------------------------------------------------
Case 1: Archimedes Spiral (Flat):

          Let R = Ave Radius  
              N = Number of Turns
              w = Width of Winding            


           |   R    |      N Turns 
      o o o o o o   |   o o o o o o 
      |    W    |   |


     L = (R^2)*(N^2)/(8*R+11*W)   (R^2 = R*R)


------------------------------------------------------------------------

Case 2: Helical Primary:

                |<- R ->|
            --  o       |       o
            |   o       |       o
                o       |       o 
            L   o       |       o  N Turns
                o       |       o 
            |   o       |       o
            --  o       |       o

      L = R^2*N^2/(9*R+10*L)  (Vertical Helix)

------------------------------------------------------------------------

Case 3: Inverse Conical Primary:

                                     
                                    / \  
    --  o                          /    o
     |   o                        /    o
     |    o   N turns            /    o
           o                 Z  /    o
     h      o                  /    o   /
             o                /    o   /
     |        o              /    o   /  Angle = X
     |         o              \  o   /   
    --          o               o    ------------
                        |
        |   w   |   R   | 
                        |
            |<--  W  -->| 
                        ^
                 Center | Line

          Z = Coil Width (hypotenuse length)
          X = Angle of Cone
          h = Z*sin(X)  Effective vertical Height
          w = Z*cos(X)  Effective horizontal Width        
          W = R + w/2   Average horizontal Radius


     L1 = W^2*N^2/(9*W+10*h)  (Vertical Inductance Component)

     L2 = W^2*N^2/(8*W+11*w)  (Horizontal Inductance Component)

      L = SQRT[(L1*Sin(X))^2 + (L2*cos(X))^2]  

------------------------------------------------------------------------
Safe coilin' to you, Dave! Hope to see you and Richard later this month!

-- Bert --

==========================================================================


>
>also, what is the mutual inductance between the two coils have to 
>be?.......or can it be anything?....it doesnt matter does it?

In general, the coupling coefficient needs to be between 0.1 to 0.2 .

This depends on many variables such as gap type, the dimensions, of the
primary and secondary, power...  We are starting to understand how such
things could be calculated but those formulas are far from ready for
general use.  John Couture's JHCTES program makes a good attempt at
designing this for you.  You can contact him at
<couturejh-at-worldnet.att-dot-net> to get the program if you wish.  I would
suggest moving the secondary up or down to adjust the coupling to get the
best performance.
	If the coupling is too low, the coil will have poor output power.  If it
is too high, the secondary may arc along the surface (bad) and the caps and
gap are put under greater stress due to poor quenching.  Also the output
power will again decrease.

	Terry



>alex
>
>