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Re: [TCML] Project Hathor 2000 Volt Test Fire

```On 2/28/16 10:27 AM, Brian Hall wrote:
```
```The time constant or tau of an RC circuit = resistance in ohms times capacitance in farads.  Then you take that R*C=tau time in seconds, and five of those time units, 5 tau, is the charge or discharge time period.
1560uf is .00156 F and at discharge time let's say the resistance of the discharge part of the circuit is very low, say .001 ohm (but you can check with a meter of course) then tau would be .00156 Farads * .001 Ohm = .00000156 seconds or 1.56 microseconds for tau, giving a 5*tau = 7.8 microsecond discharge time in this example.

```
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```
Most of these kinds of circuits, though, are RLC, and the L will dominate over the R.
```
```
I would start with assuming a resonant frequency of 1/(2*pi*sqrt(LC)), and the pulse will likely be the first quarter cycle.
```

```
```Current through a capacitor as it discharges can be found with a differential equation (rise over run) of i = change in voltage/change in time.
Let's say the change in voltage is 0 to 2000, and the discharge time of 5 tau is 7.8 microseconds, then with a 0-2000 voltage rise on the y axis and a 0-.0000078 second run on the x axis, 2000 volts/.0000078 seconds = 254,410,256 amps.

At least that's what I recall from the circuit analysis class I am presently taking.  We haven't quite covered RLC circuits yet (just RC and RL)  and the inductance of the coil also likely has an effect on the discharge time.  Chances are the resistance in your discharge circuit isn't quite as small as this example.  Anyone, please correct where I'm wrong.

Brian Hall

________________________________________
From: Tesla <tesla-bounces@xxxxxxxxxx> on behalf of jimlux <jimlux@xxxxxxxxxxxxx>
Sent: Sunday, February 28, 2016 11:44 AM
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Project Hathor 2000 Volt Test Fire

On 2/27/16 11:35 PM, 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.

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.

```
```

Do you have an oscilloscope?

With just a simple loop of wire somewhere in the vicinity, you can get
an idea of what the current waveform looks like (duration and shape),
without knowing the actual values.

Once you know that, you can start to estimate the peak current, which
would allow you to figure out how to make a current transformer, or shunt.

```
```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#)'

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