Re: Larger than LTR cap

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

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
 >
 >