Re: [TCML] 8 inch tesla coil design

["David Rieben" <drieben@xxxxxxxxxxx>]

Jeremy,

As DC mentioned, you may get a erratic firing out of a STATIC
spark gap with that much C from a 15/120 NST power supply.
If you were using a SRSG, then you could go considerably higher
into the LTR zone without suffering this effect and consequently,
get longer output sparks. Since you are using a static gap, you defnitely
want to stay away from near resonant size with you primary cap
as the R voltage rise can make a boat anchor out of your NST in
short order, especially if you open the primary SG too wide!
Then again, if everyone used restraint and kept their SGs narrowed
to a reasonable width that was comensurate with the rated output
voltage of the NST, it seems that there should not be a problem
with ressonant voltage rise smoking the transformer (or the capacitor).
Of course, for coilers, that is obviously a tall order, though. ;^)

David Rieben





----- Original Message ----- 
From: <jeremyee@xxxxxxxx>
To: "Tesla List" <tesla@xxxxxxxxxx>
Sent: Thursday, September 09, 2010 9:30 PM
Subject: Re: [TCML] 8 inch tesla coil design


> So the rule of thumb of using only a 3:1 aspect ratio for secondary 
> diameters of 8 inches or more is no longer recommended? It has been 
> several years since I looked at this. Thanks for the input.
>
> Also, David, I am using an MMC and to up the capacitance I could put 
> another string in there. It would raise the capacitance from 30 nF to 45 
> nF. Can an NST handle charging this load or will I get erratic behavior 
> out of my static gap?  The LTR recommended for my power supply is about 35 
> nF. Thanks again for the inputs!
>
> Jeremy
> Sent from my BlackBerry device from Cincinnati Bell Wireless
>
> -----Original Message-----
> From: DC Cox <resonance@xxxxxxxxxxxx>
> Sender: tesla-bounces@xxxxxxxxxx
> Date: Thu, 9 Sep 2010 14:22:43
> To: Tesla Coil Mailing List<tesla@xxxxxxxxxx>
> Reply-To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Subject: Re: [TCML] 8 inch tesla coil design
>
> 3.5:1 is ok.  4.5:1 will provide better performance.
>
> I usually shoot for 10-12 turn pri, so you might wish to add a small 
> amount
> of capacitance, but your 14 turn pri should also work very well.
>
> Dr. Resonance
>
>
>
>
> On Wed, Sep 8, 2010 at 7:59 PM, <jeremyee@xxxxxxxx> wrote:
>
> > Hey group. It has been a long time since I have been on here and I wanted
> > to pass a design by you guys to see if I have anything weird. Below are 
> > some
> > inputs to and outputs from TeslaMap:
> >
> > 15 kV, 120 mA NST bank
> > 30 nF MMC
> > 8.625 inch secondary with 1160 turns of #23 magnet wire (74 mH)
> > 6 in by 30 in toroid (31.6 pF)
> > Tuned primary at 14 turns for 112 uH
> > Resonant at 87 kHz
> >
> > One of my main concerns is sizing the toroid for maximum breakout voltage
> > but keeping the number of primary turns down to minimize resistive 
> > losses.
> > At 14 turns I feel like I am a little too high. I am using a static gap 
> > with
> > about 6 parallel copper couplings. My secondary aspect ratio is about 
> > 3.5:1
> > (is this ok?). I really appreciate any insight into my design. Thanks!
> >
> > Jeremy
> > Cincinnati, OH
> > Sent from my BlackBerry device from Cincinnati Bell Wireless
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
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