[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Subject: Overheated Secondary
Hi Phil,
VA is simply transformer ratings. It would be ideal to use actual wall
plug power measurements. But since I use this in a design program, VA is
as close as I can get beforehand. For all practical purposes, it won't
vary enough to make a significant impact on spark length.
The equation is simply a refinement of John Freua's spark length
equation, 1.7 x sqrt(W). This equation specifically states that spark
length changes with input power. What you don't see in that equation is
that it is based on 120 bps and on whatever losses were occurring in
John's test systems, and it's been a good ballpark for years. I wanted
to factor in various cap sizes, various bps, cap charge time, cap
voltage, and input power into the equation.
Here are detailed ingredients to the following equation:
-----------------------------------------------------------------------
Spark Length (inches) = sqrt(VA) + (sqrt(eJ x BPS x 1.263) x .75)
Where:
VA = volt amps = transformer ratings
BPS = breaks per second.
eJ = effective cap energy in joules = 0.5 x C(tank) x eVp^2
eVp = effective cap peak voltage = x_vp*(1-pow(2.7182818,(-rsg_fr/rsg_t1))).
x_vp = transformer peak output voltage.
rsg_fr = rotary gap firing rate (1/bps).
rsg_t1 = time for cap to charge to one time constant.
The .75 is a conservative loss factor (inserted at the bang energy portion).
-----------------------------------------------------------------------
You won't see a major change in spark length, but you will see
variations with time and energy.
Here are some comparisons to the JF equation and I think you'll find
this equation is very conservative (if anything):
In all cases = 12kV rating, 60Hz, 120V input
I will show mA increase for various cap sizes through 120bps, 240bps,
480bps.
BTW, if the table is messed up in formatting, here is what it looked
like before I sent it.
http://www.classictesla.com/temp/Spark%20Length.txt
Take care,
Bart
Cap BPS mA Bart JF
-------------------------------------
0.01uF 120 30 28.7" 32.3"
0.01uF 120 60 37.7" 45.6"
0.01uF 120 90 43.9" 55.9"
0.01uF 120 120 49.0" 64.5"
0.01uF 120 300 71.1" 102"
0.03uF 120 30 28.6" 32.3"
0.03uF 120 60 41.2" 45.6"
0.03uF 120 90 49.7" 55.9"
0.03uF 120 120 55.9" 64.5"
0.03uF 120 300 79.2" 102"
0.05uF 120 30 27.4" 32.3"
0.05uF 120 60 40.8" 45.6"
0.05uF 120 90 50.5" 55.9"
0.05uF 120 120 58.0" 64.5"
0.05uF 120 300 84.4" 102"
Cap BPS mA Bart JF
-------------------------------------
0.01uF 240 30 29.1" 32.3"
0.01uF 240 60 40.6" 45.6"
0.01uF 240 90 47.8" 55.9"
0.01uF 240 120 53.4" 64.5"
0.01uF 240 300 75.7" 102"
0.03uF 240 30 26.9" 32.3"
0.03uF 240 60 40.4" 45.6"
0.03uF 240 90 50.4" 55.9"
0.03uF 240 120 58.3" 64.5"
0.03uF 240 300 86.3" 102"
0.05uF 240 30 25.6" 32.3"
0.05uF 240 60 38.8" 45.6"
0.05uF 240 90 49.1" 55.9"
0.05uF 240 120 57.8" 64.5"
0.05uF 240 300 90.7" 102"
Cap BPS mA Bart JF
-------------------------------------
0.01uF 480 30 28.0" 32.3"
0.01uF 480 60 41.2" 45.6"
0.01uF 480 90 50.4" 55.9"
0.01uF 480 120 57.3" 64.5"
0.01uF 480 300 82.0" 102"
0.03uF 480 30 25.1" 32.3"
0.03uF 480 60 38.1" 45.6"
0.03uF 480 90 48.4" 55.9"
0.03uF 480 120 57.2" 64.5"
0.03uF 480 300 91.6" 102"
0.05uF 480 30 23.9" 32.3"
0.05uF 480 60 36.2" 45.6"
0.05uF 480 90 46.2" 55.9"
0.05uF 480 120 54.8" 64.5"
0.05uF 480 300 92.1" 102"
FIFTYGUY@xxxxxxx wrote:
Is this "VA" the nominal open-circuit voltage times the nominal
short-circuit current of the power supply?
If so, why would this matter (past a certain point with a SRSG, or past
another point with a RSG)? If I plug my primary into the local
overhead power
line, neither the bang energy nor the BPS will be any different than if I
use, say, a PT. And even then, once we get a big enough power supply
that is
1:1 "resonant" with the primary cap, how much more gain is to be had?
But from your equation, using a power supply with 100 times a
"reasonable" VA rating would always yield a significant
*multiplication* of spark
length.
-Phil LaBudde
Center for the Advanced Study of Ballistic Improbabilities
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla