Re: Larger than LTR cap

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

Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org> 

A little late, perhaps....  But using a multiple-layer primary will also 
reduce overall primary size.  We (Steve Ward, actually) used it on our 
latest TTCT with good results.  I'm not sure if any of the current design 
programs (perhaps acmi or inca?) will calculate the inducance of a stacked 
pancake primary, so trial and error may be the best recourse.

Mark Broker
Chief Engineer, The Geek Group

On Fri, 20 Feb 2004 17:51:26 -0700, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> Hi Chris,
>
>As Terry said, Static LTR is about 9.2 nf.  Increasing Cp to this value will
>help somewhat,  To reduce the physical size of the primary and keep the
>secondary freq the same, there are several possiblilities:
>
>1. Go larger than static LTR to reduce the number of turns.  This will
>reduce the performance somewhat and the BPS.
>
>2. Use smaller diameter primary wire and spacing to make the primary more
>compact.  Javatc will help in the retuning and affect on the number of
>turns.  My guess is the peak current will permit this.
>
>To reduce the physical size of the primary by increasing the resonant
>frequency of the secondary, there are several possibilities:
>
>1. Reducing the topload capacitance (may affect performance).
>
>2. reducing the number of turns (reduce the aspect ratio),
>
>3. decreasing the diameter of the sec (less inductance per turn).
>
>4. using a thicker wire on the sec.
>
>Don't know where your design is in terms of the 5:1 aspect ratio, number of
>turns, and topload breakout relative to topload voltage.  Certainly, as
>Terry said, increasing the thickness of the wire can reduce the Ls.  If the
>aspect is maintained, the number of turns will be reduced.  If the number of
>turns is maintained the aspect will increase.  I have heard that small coils
>can have a somewhat larger aspect than 5:1.
>
>Gerry R
>
>
>  > Original poster: Chris Roberts <quezacotl_14000000000000-at-yahoo-dot-com>
>  >
>  > Hello everyone,
>  > It's been a while since I asked a newbie question so I guess it's about
>  > that time again. =D I am designing a new mini coil using a 9/20 nst. The
>  > LTR tank size therefore is quite small. (.0088 uF) This blows the required
>  > primary turns sky high, making the necesary diameter of the primary quite
>  > large, defeating the purpose of it being a mini coil. So would there be
>any
>  > consequences if I stretched the value for the tank cap to, say, .0125 uF?
>  > This would also save the number of geek caps that I have to stuff under
>the
>  > base. Any thoughts?
>  >
>  >
>  > -Chris
>  >
>  >
>