Re: H/D ratio

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

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

In a message dated 1/15/04 10:34:31 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:
Original poster: "Luke" <Bluu-at-cox-dot-net>

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

Hi Luke,
     Don't confuse "maximum inductance" with "best size". Actually, in a 
solenoid coil, the maximum inductance for a given length and diameter of 
wire occurs at h=0.9r. IIRC a paper on maximizing inductance was posted to 
the list in April 2002. In such a design, a 20-inch diameter coil would be 
only 9 inches high! The voltage gradient along the coil would be extreme, 
(~50 kV/in), and a toroid sitting only a foot or so above the primary of 
such a coil would preclude the possibility of any arcs except to the 
primary.  Such low ratio coils might have some application in magnifier 
designs, but for a standard TC it's just not practical. Like life, a Tesla 
Coil is a balance between many conflicting desires.

Matt D.