Re:

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

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

Hi Chris,

I know your running a lower voltage, and can allow the use of a larger cap 
size, but the coil length to spark length needs to be considered. 200nF 
will certainly burn up the coil. The coil is only 22 inch in length. If I 
were you, I would shoot for a target of a random sparklength at about twice 
the coil length. Lets say you want roughly twice that length (approx 50"). 
I would then recommend something hovering around 20nF, which isn't far off 
of your original cap size. In fact, you may want to try this with your 
original cap before going onto a larger cap. I also recommend the use of a 
variac to control the input voltage to the MOT stack so that "you" have 
physical control of the MOT's output voltage and can ramp up as needed. 
You'll probably find the length you desire at about half the input voltage.

Take care,
Bart

Tesla list wrote:

>Original poster: "Chris the great" <downnessisgoingup-at-hotmail-dot-com>
>The main reason for the cap size is the output current on the transformer.
>The number of primary turns will be around 4, meaning I may have problems 
>with primary arcing.
>However, I am not sure if 200nF is a good idea, ss I could experience alot 
>of secondary arcing at that power level.
>I am new at this, and 200nF DOES seem to be on the large (huge) size for 
>my coil, however, would it work?  Or would my coil destroy itself?
>Should I keep cap size to perhaps 50-100nF at the very maximum?
>
>Chris
>
>
>
>>From: "Tesla list" <tesla-at-pupman-dot-com>
>>To: tesla-at-pupman-dot-com
>>Subject: Re: Date: Sun, 16 Nov 2003 11:36:31 -0700
>>
>>Original poster: Bart Anderson <classi6-at-classictesla-dot-com>
>>
>>Hi Chris,
>>
>>Are you sure you want to run a 200nF cap size? That's on the huge side 
>>for a 4.5" coil. Have you looked at the number of turns required on the 
>>primary when using a cap of this size? Also, the cap energy is going to 
>>be way up there for a coil this size. I run between 20nF and 80nF on my 
>>10KVA pig. David Rieben runs 85nF on his. These are just a couple higher 
>>powered coils for reference. BTW, these are roughly 13" diameter coils. 
>>What made you consider a 200nF cap? Was it the transformer output current?
>>
>>Take care,
>>Bart
>>
>>> > Original poster: "Chris the great" <downnessisgoingup-at-hotmail-dot-com>
>>> >
>>> > I have done some work on my coil since I have last posted, and I have
>>>found
>>> > my problem.  I think my tank cap is WAY to small for my MOT power source,
>>> > which will soon be a 4 MOT stack.  I have calculated (from
>>> > http://home.earthlink-dot-net/~electronxlc/tccalc.html) that my tank 
>>> capacitor
>>> > should be 200nF at 8kV, 650mA, not 13nF.
>>> > I would like to make sure that this is indeed a good tank cap size, so I
>>> > don't go and make a huge poly capacitor for nothing (actually 3 in
>>> > parallel).  Or would another type of capacitor be easier to
>>>transport/make,
>>> > or cheaper, or better?
>>> >
>>> > Needless to say I will need a very large topload, I was thinking about a
>>>40
>>> > inch toroid on top of a 24 inch toroid, for a total secondary capacitance
>>> > of 77.6pF, with an inductance of 19.6mH.
>>> > My primary inductance will be very small, however I have found that a
>>>lower
>>> > primary inductance produces brighter sparks that are slighly longer.  I
>>> > will have 2 series static sucker gaps, until I can get a rotary gap.
>>>More
>>> > on my coil here
>>> > http://hot-streamer-dot-com/chris/4inchcoil.html
>>> >
>>> > Are these good values for my 4.5 inch coil?  I expect a major increase in
>>> > performace over my 12 inches of spark so far, but will they be around
>>> > optimum values?
>>> >
>>> > Thanks!
>>> > Chris
>>> >
>>> >
>
>
>
>