Re: Primary / Secondary Diameters

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Parpp807-at-aol-dot-com>

> I posted a few days back a question about primary / secondary diameters for a
> bipolar
> coil. I am getting ready to form the primary coil for my 48 inch, 4.5 inch
> diam bipolar
> secondary. Is there a way to determine what the diameter of the primary helix
> should be. My experience with a 20 inch bipolar is that the primary can get
> no closer than 1.5 inches
> from the secondary without arcover. But is this all trial and error, is there
> no way to
> determine this?

Determine it from the required coupling coefficient. Use Paul
Nicholson's
acmi program (http://www.abelian.demon.co.uk/tssp)
to evaluate the inductances and the coupling coefficient 
from the dimensions of the coils. The ideal coupling coefficients are 
obtained from the formula:

k=(b^2-a^2)/(b^2+a^2)

where a and b are two integers with odd difference. The most usual 
combinations are obtained with b=a+1. Total energy transfer is obtained
in b/2 cycles.
Ex: a=6, b=7 results in k=13/85=0.153

For usual k values, of less than, say, 0.18 (mode 5,6), the clearance 
is probably enough to avoid sparking.
In the calculations, consider the full secondary and the full primary.

Antonio Carlos M. de Queiroz