RE: RE: [TCML] Toroid Problems

["Lau, Gary" <Gary.Lau@xxxxxx>]

Ahh, that's the "interesting" thing about designing a Tesla coil.  Everything is a trade off.  There is no simple answer to any of that.

A higher inductance primary has the advantage of possibly offering lower spark gap losses due to lower primary current.  A higher capacitor value offers a bigger bang size that may result in longer sparks, but if it's too big, the NST will draw excessive current.  A bigger toroid often results in longer sparks, possibly because it holds a larger reservoir of charge to feed the streamers, or perhaps because it requires a comparably larger primary or cap value.  But if the toroid is too big, it won't break out.  Since tapping your cap to a larger value and adding a couple more primary turns are both low cost options, try each, one at a time, and let us know which works better!

Coilers commonly use the peak NST voltage (9000 x 1.414 = 12.7kV in your case) as the cap's DC voltage rating, and failures from over-volting caps is something we just don't hear of anymore.  I think the advice you heard may have originated from a source which stands to gain if you buy more caps ;-)  The cost is of a cap is proportional to the voltage rating, squared. If you operated your coil for many hours every day, you might see a failure (it was experimentally determined that the life expectancy at this voltage rating is about 75 hours), but for hobbyists who run their coils just a few minutes at a time, 75 hours is a very long time and it's just not a problem.  Again, a trade off between cost and longevity, and you get to choose.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Nicholas J. Goble
> Sent: Tuesday, August 05, 2008 3:56 PM
> To: Tesla Coil Mailing List
> Subject: Re: RE: [TCML] Toroid Problems
>
> What would be the best way to tune my coil, without limiting my
> performance?  In other words, what would be worse: larger primary,
> smaller caps, or smaller toroid?
>
> Also, would tapping my caps be unsafe?  I was told that my MMC's
> voltage rating should be 2-3 times my NST's output.  If I tap my MMC,
> will that be unsafe?
>
> Nicholas Goble

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