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Re: More real experiments
Richard Hull wrote:
> Well gang,
>
> I have been busy over the weekend with my Pearson current monitor and
> capacitive HV voltage divider. I physically measured the voltge across
> the gap and current through it while the coil was in operation. In an
> effort to find the power consumed by the gap in operation.
[snip]
> Analysis:
>
> Due to my using a variac and only allowing the AC line voltage to reach
> 28 volts in to the neon's primary, I measured a peak voltage out from the
> transformeers secondary of 2640 volts.
>
> This showed up as the max voltage across the non-firing gap. Firings at
> the gap showed a rather immediate fall to ~200 volts. The current
> transformer indicated a peak current in the system at this point of ~80
> amps. Thus under the optimal conditions the gap had a lowest possible
> resisitance of 2.5 ohms. (The gaps were hardly making any noise!) For the
> instant of max turn on, the gap consumed 16,000 watts of peak energy.
> The peak tank energy in our little 15VA system would have been on the
> order of 160,000 watts. based on a 2KV firing point and 80 amp tank
> current. 10% losses figured this way.
>
> The scope was set up to yeild a mathed third trace as A X B yielding
> volt amps. This was intergrated by hand with time to yield a total sine
> consuption of energy on the order of 1.6VA. With the power factor
> corrected primary hooked to a watt meter we read 15.1 VA while the system
> was on (auto integrating). This shows that we lost about 10% of the
> input energy in the gap on average. Another cross confirmation.
Interesting experiment! Did you try the same msmt at other power levels?
I'm curious as to how the arc resistance will vary as the current is increased.
On your six-gap tungsten sparkgap, what was the total gap distance?
To add another data point, I tried a similiar msmt on my coil, and came up with
a total gap resistance of 0.65 ohm for a 4-gap system, at about 1.8 kA.
The total gap distance in this case was 0.060". I would've expected the
0.65 ohm value to be much smaller, since the arc channel is supposed to get
fatter as the current increases, but apparently it doesn't grow so fast after all.
I was expecting a gap resistance of 0.25 ohm! If I had known these numbers before
I had built my coil, I would have laid out the primary ckt quite differently, so
that it would've had a larger impedance [SQRT(L/C)].
-GL