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Re: [TCML] Subject: Overheated Secondary


Ok, it doesn't affect the spark length as much
as I thought it would, though. I didn't realize
that the math worked out like this either. I was
just assuming that the spark length was a simple
result of the sqrt(power) x 1.2 and the power was simply a factor of the bps x C, in joules. I
guess that's what I get for assuming ;^) Also, I
am a little surprised that you are actually running
an NST coil STR, considering the prevailing
school of thought about LTR operation for the
fragile NSTs in the last decade.
Spark on,
David Rieben

----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, January 05, 2008 3:04 PM
Subject: Re: [TCML] Subject: Overheated Secondary

Hi David,

Yes it would.

If I used a .075uF cap size at 120 bps in say an SRSG setup: = 6.48j x 120bps = 778W. If I used a .019uF cap size at 120 bps is say an SRSG setup: = 2.13j x 120bps = 256W.

For spark length, I use the following:
Spark Length (inches) = sqrt(VA) + (sqrt(eJ x BPS x 1.263) x .75), (.75 is as a loss factor).

In the case of the .075uF, sqrt(2120)+(sqrt(6.48*120*1.263)*.75)= 69.6"
In the case of the .019uF, sqrt(2120)+(sqrt(2.13*120*1.263)*.75)= 59.5"

My coil runs about 60" spark length on average, so it's exactly as I would expect it to.
For a cross check, the JF equation would show 66" in both cases.

The reason I use the above equation is that it accounts for bang energy. Someday I may insert a cap into LTR mode on this coil, but not today.

Btw, Javatc had a similar sqrt(2) issue in the rsg and static gap spark length fields (noticed while checking my math). This caused the output spark length value to be high by a factor of 1.4. I corrected that and pushed Javatc to version 11.5 on the web and pc download zip file. I also found my script editor kept changing the Omega symbol when it read in the file, so I simply put that back to text "Ohms" as it use to be.

Take care,

David Rieben wrote:
Hi Bart,

Am I reading that right? You're running an NST coil at 2.7X
LOWER or smaller than resonance? Wouldn't that really limit
your bang energy?

David Rieben

Hi Wyatt,

I'm running my NST coil about 2.7 times lower
than Cres with no problems (safety gaps, gap widths, etc. are of course important).

Take care,

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