Re: Number of turns for a secondary?

• To: tesla-at-pupman-dot-com
• Subject: Re: Number of turns for a secondary?
• From: Hollmike-at-aol-dot-com (by way of Terry Fritz <twf-at-verinet-dot-com>)
• Date: Sun, 03 Jan 1999 12:40:56 -0700
• Approved: twf-at-verinet-dot-com

In a message dated 1/3/99 3:00:04 AM Mountain Standard Time, tesla-at-pupman-dot-com
writes:

> 
>  This thread has made me curious as I plan on winding a larger diameter coil
>  soon myself. I always thought that you decreased the gauge of the wire (
> fewer
>  turns per inch) to keep the H/D ratio compatible with the number of turns
>  (ideally somewhere between 4:1 or 5:1 & under 1000 turns). I thought that 
> was
>  why (aside from the current being carried) the larger coils always used a
>  heavier gauge wire. Like I said I'm just curious & I know a lot of other
>  factors come into play in the design. Thanks,  Jim
>  
Jim,
    According to one reference I have  the maximum inductance of a single
layer solenoid coil occurs when the H/D ratio is 2.46:1.   I once did a long
drawn out calculation(based on the Wheeler equation) that showed this to occur
at a ratio of 2.22:1.   My calculation was based on a fixed length of wire, so
the number of turns went down as the diameter goes up.  It seems to be in fair
agreement with the text.
    This doesn't mean that that is the best design for Tesla coils though.
One still has to consider the coil's self capacitance and it's ability to
withstand the high voltage difference between each end(probably the most
important aspect in the design criteria).  This is probably why most coilers
design them with H/D ratios from 4:1 - 6:1.   
Hope this helps,
Mike

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