User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0 SeaMonkey/2.39
Assuming that the equivalent resistance of your capacitor string is
relatively low, your capacitor bank and HV cap will ring like an LC
circuit (at least for the 1st quarter-cycle). If you can estimate the
inductance of your work coil, you can do a first-cut estimate of the
peak coil current by assuming that almost all of the initial energy
(0.5*CV^2) was transferred to your work coil 0.5*LI^2) 1/4 cycle later.
You can estimate your work coil inductance by using the inductance
formula for an Archimedes spiral:
R1 = innermost turn radius
R2 = Outermost turn radius
Rav = R1 +(R2-R1)/2 = Average Radius
N = Number of Turns
W = R2-R1 = Coil Width
L = (Rav^2)*N^2/(8*Rav+11*W)
"Guesstimating" the dimensions of your work coil, the inductance appears
to be around 3 microhenries.
Assuming no resistive losses, the estimated peak current would be:
I = V*Sqrt(C/L) amperes
With a 1560 uF cap bank charged to 2000 volts, the estimated peak
current would be about 45 kA(!)
In reality it will be substantially less (perhaps 1/2 to 1/3 of this)
due to the equivalent losses from series resistance of your electrolytic
caps, wiring, switch, and work coil resistance AND some of the energy
from the ringing LC system is converted to kinetic energy in the
aluminum disk. The energy transferred to the disk can be estimated by
measuring the peak height of the ring and the mass of the ring.
The ringing frequency can be estimated (C in farads and L in henries) :
F = 1/(2*Pi*Sqrt(LC)) in Hz
So, for your system, F is about 2.2 kHz
The period will be 1/F seconds, and the first current peak will occur at
1/4*T seconds, so your current peak occurs about 107 usec after your HV
switch closes.
You'd need to use a current transformer and oscilloscope to accurately
measure the current.
BTW, at the first current peak, all of the system energy resides in the
magnetic field around the work coil. As the coil current then starts
decreasing, the capacitor current reverses and the coil attempts to
reverse-charge your capacitor bank. This is not a problem with film or
paper capacitors, but your electrolytic capacitors are polarized, so
they may not always handle being abruptly reversed-charged in a graceful
manner. To prevent undesirable "surprises" and to extend capacitor life,
many folks install high-current diodes across the capacitors to prevent
them from being forced to conduct high reverse currents.
Good luck and play safely,
Bert
krux@xxxxxxxxxx wrote:
So brief little update on Hathor, the ring launcher I built. We did a full
power test fire last night. And apart from breaking most of the wire ties
holding the coil in place, everything worked nicely.
https://www.youtube.com/watch?v=iFurvAEPmZg
Main project page is here:
https://krux.org/article/Project_Hathor
Now of course, that I have this fine scientific insturment, I'm curous of a
good method of meauring how many amps this thing produces when it fires, what
the disharge curve looks like, etc..
So 2000 volts, at 1560 uF, or 3120 Joules.
I'm guessing I can take the energy in Joules, some how measure how long it
takes to fire, which will give me how many watts. Then it's a simple matter
of Ohms law to figure out my amperage, or at least amperage averaged over the
time it took to fire.
Any ideas, or other data points that would be useful to have here?
perl -e 's==UBER?=+y[:-o]}(;->\n{q-yp-y+k}?print:??;-p#)'
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
--
Bert Hickman
Stoneridge Engineering, LLC
http://www.capturedlightning.com
***********************************************************************
World's source for "Captured Lightning" Lichtenberg Figure sculptures,
magnetically "shrunken" coins, and scarce/out of print technical books
***********************************************************************
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla