Re: H/D ratio

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 1/15/04 7:34:31 AM Pacific Standard Time, 
tesla-at-pupman-dot-com writes:


>I found on the net in a few places stating that the maximum amount of
>inductance from a coil is when the height is the same as the
>diameter.  This is a 1:1 ratio.
>
>If that is the best inductance ratio then why is this ratio not used for
>the tesla coil secondary to take advantage of a high inductance ratio
>between the primary and secondary?
>
>Luke Galyan
>Bluu-at-cox-dot-net


Luke,

I am not sure what that reference is about.   A 6" diameter coil wound with 
say # 22 wire with a 30" winding length will have about 31.4 mh of 
inductance.  The same 6" diameter coil with a 6" winding length would have 
about 4.7 mh of inductance.

Maybe they mean for a given height, that when h = d, the inductance is 
maximum.  The Wheeler equation does not seem to show that however.  For 
example the same 6" diameter coil as above with the following winding lengths:

5" = 3.7 mh
6" = 4.7 mh
7" = 5.8 mh

You would have considerable problems with a 6" high secondary with strikes 
to the primary.  Short, fat secondaries can be used as the third coil on 
magnifier since you can locate it remotely, away from the primary and 
driver coil.

Ed Sonderman