Re: HF sparks

From: 	Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
Reply To: 	elekessy-at-macquarie.matra-dot-com.au
Sent: 	Saturday, August 02, 1997 5:34 AM
To: 	Tesla List
Subject: 	Re: HF sparks

Tesla List wrote:
> From:   John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
> Sent:   Thursday, July 31, 1997 5:18 PM
> To:     Tesla List
> Subject:        Re: HF sparks
> At 01:30 PM 7/31/97 +0000, you wrote:
> >
> >From:  Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
> >Reply To:      elekessy-at-macquarie.matra-dot-com.au
> >Sent:  Thursday, July 31, 1997 7:18 AM
> >To:    Tesla List
> >Subject:       Re: HF sparks
> >
> >Richard,
> >
> >>From my own observations so far and from other peoples posts I am
> >inclined to agree with all of your points except number 3. In the past,
> >folk seemed to have built Tc's using the clasic formula for Capacitance
> >vs input power and these have have been good performers. Recently
> >though, Bert pool and others seem to have been using relatively small
> >caps with higher break rates and getting very impressive results.
> >
> >Maybe not quite in the same league but I have recently re-fitted my 3
> >1/2" 15KV 60Ma TC with a .01uF cap after blowing up my .015uF earlier.
> >After re-tuning the primary, the forced air gap seems to fire faster but
> >the length or appearance of the sparks seems to be the same (about 30"
> >with my present  20" by 8" toroid).
> >
> >I am about to wind a new 6" secondary and I intend to leave all other
> >parameters the same so it will be interesting to see if the lower freq.
> >produces a longer spark?
> >
> >Cheers, Peter E.
> >
> >-------------------------------------------------------------
> >
>     Peter E.
>   Try using 365 KHZ for your operating frequency. This is a possible optimum
> frequency for 900 watts input that coilers have used in the past. This comes
> from the equation
>        KHZ = 3032.5 x W^-.2767 - 96.4       W = watts input
>   The primary and secondary tank parameters would be found using the equation
>       KHZ = 1/(6.283 sqrt(LC))
>    Design the system so it can be adjusted in operating frequency about plus
> or minus 20%. Test using spark length. Post your results on the T. List. You
> will be the first person to determine if the coilers in the past were doing
> it right.
>     John Couture
> >


According to the WinTesla program, my coil is already running at around
this freq ~ 320Khz with my approx 18Pf toroid (8" by 20") and 22" by
3.5" secondary with 840 turns 22# wire. These parameters result in 30"
max sparks. I will try the old led/signal generator trick to see if this
is right but maybe you can plug these values into your magic program and
see if it agrees.

I have done some experiments substituting a 22" sphere for the toroid
(around 30pf by my estimation) and the primary tuning changed
considerably (8 turns to 11 turns) so I gather the freq would have
dropped by at least 20%. The result was an increase in spark length to
33" but the sparks were harder to control i.e. they mostly struck the
strike rail on the primary or the ceiling.

All of this still leads me to believe that lower freq. and/or greater
secondary capacitance still gives you longer spark, but I am open to
alternative arguments.

Cheers, Peter E.