Re: New coil

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi John,

Tesla list wrote:

>Original poster: "John Richardson" <jprich-at-up-dot-net>
>Hi Bart,
>
>Thanks for the tips.  I was using the Geek chart, and I assumed that it was
>on the money as far as NST safety goes.  Is this not so?  Regardless, I'm
>going to start doing the calculations manually, or try your MMC program.

My JavaMMC program is linked at the Geek Group website. Although I've moved 
the program to a different directory  and have sent the Geek Group my 
program to load on their own server at their discretion, last week I placed 
a redirect to the JavaMMC program for their old link (if it's still there). 
This will take you to the latest program regardless.
http://www.classictesla-dot-com/java/javammc/javammc.html

The last changes made to the program use the same equations as which the 
Geek MMC chart was developed, so you should end up with the same value. My 
program will give quite a bit more information other than the cap value. It 
will show rms current, total tank voltage, and those type of items for 
consideration when designing the cap bank.

Many have built and run MMC cap banks right from the Geek chart without any 
problems. Failure rate is nearly null (or is not being reported). RMS 
current is a key factor for MMC health and longevity. The reliability 
rating shown in JavaMMC is based on the rms current, but it is not based on 
the tank voltage. The reason I didn't throw a derating factor there is 
solely because of the excellent success of building and running MMC's at 
these minimal voltage ratings.

I, as mentioned, am part of the crowd that likes to derate the tank voltage 
(regardless). Ideally, I would derate by 2.5 x the transformer V. This is 
extreme for an  MMC, but it is standard business for other cap banks. This 
is why I said  "if it was me, I would go 2 x the NST voltage". It is really 
a choice that you should decide if it's right for you. What is right for 
one person, may not be for the next  (cost, coiling activity, etc..). I 
understand that and is why I don't push the issue. I, however, do what I 
think is right for "me".

Something worth consideration on this matter is the power supply current. 
If you have a beefy transformer, small cap size, and mis-adjusted gap (or 
problem), you could very easily increase the voltage at the cap beyond even 
an MMC's ability is (and a good reason to ensure you have a safety gap 
across the spark gap). A beefy transformer (PT, PDT, NST farms, MOT's) in 
comparison to cap size would be a good reason to throw in a little 
over-volt precaution into the design (my opinion, of which you may find I 
have many).

Take care,
Bart