Re: Fw: Capacitor Help (primary coil turns, cooling motor)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "MalcolmTesla" <tesla@xxxxxxxxxxxxx>

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, December 21, 2005 12:59 AM


> Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
>
> Hi Malcolm,
>
> Tesla list wrote:
>
> >Original poster: "MalcolmTesla" <tesla@xxxxxxxxxxxxx>
> >
> >BTW - does this mean my coil is running very weak even when I get it
tuned?
>
> No.
>
> >I thought I saw someone say in the past an NST powered Tesla Coil should
be
> >tapping around turn 9 to 10 on the primary otherwise it's not running
very
> >efficient?  Any truth to that?
>
> Absolutely NOT! No such thing. But, maybe what you read was not
> interpreted as the writer intended. Regardless of NST, MOT, PIG, PT,
> or whatever power source is used, the primary frequency is determined
> by the primary inductance and the tank cap. The tank cap is
> sufficiently large enough to make the primary "not" sensitive to
> misc. changes. But the secondary is very sensitive. It is sensitive
> to external capacitance's which includes toploads, primary's, strike
> rings, etc. When I modeled your coil via the photos, I modeled the
> strike ring as well. In Javatc, this would be considered a "grounded"
> object. I used the disk input to best represent the strike ring
> (large ID and 1/4" larger OD). This is exactly why there is a check
> box for grounded or topload connection in that program.
>
> With all the components in position, the secondary or resonator has a
> resonant frequency. The primary inductance can be adjusted (as well
> as tank C) to ensure the primary circuit is at the same frequency as
> the resonator. The number of turns is a matter of geometry and
> inductance needed for resonance, nothing more. There is no magic
> turns number for any given transformer type. There is common sense,
> but no magic values.
>
> >What can I look at doing in the future to
> >bring my turns down to the 9 to 10 range?  Add more strings of caps in
> >parallel to increase capacitance?
>
> If you need to increase L for resonance, you can keep L as is and
> lower C to attain the same resonance. As a matter of fact, JAVATC is
> recently updated with a capacitance reference output (it's within the
> primary outputs section). If you give Javatc the geometric dimensions
> of your setup including the number of turns on the primary and simply
> leave the tank cap value at 0, you can run the program and it will
> let you know the value of C needed for resonance. You can certainly
> run the coil at 9 or 10 turns if desired. Just increase C.
>
> Take care,
> Bart

Thanks very much for that.  I was worried I was way off track and needed to
modify my system to get down into the 9 to 10 turn range.  You are right, I
may have just not interpreted something correctly.
I'll get some more turns added to the primary most probably tonight.
However I accidentally killed my squirrel cage motor for cooling the spark
gap.  I had removed the top cover of my box containing the primary and was
fine tuning the safety gap.  One of the HV leads from the NST slide down and
touched the case on the motor and I assume fried it.  It doesn't work any
more.  Amazingly my 4" PVC spark gap with copper tubes produced some of the
best sparks yet off the torrid and we didn't even have a cooling fan source
to quench the spark.  I'm going to have to find some other source of
cooling.  For me it has to be portable as I like taking my new coil places.

Thanks
Malcolm - KC