# Re: Recent power arc experiments

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Boris,

First, let me say that this is an ultra cool experiment!!

I think I know why the resistors stayed cool!

My testing has shown that arcs are about 220 kohm plus 1pF per foot of arc
impedance.  The nine 1500 ohm resistors are only 13.5 kohms of resistance.
Thus, most of the heat energy (95%) was being dissipated in the arc rather
than the resistors.  I have some TC output impedance data at:

http://hot-streamer-dot-com/TeslaCoils/Misc/impedance/impedance.html

that may help a bit with getting the resistors impedance matched better.
However, I think you need much more resistance.  Assuming the RMS current
is constant, the heating will be proportional to the resistance.  The 13.5
kohm was just too small.  If you can find the effective output impedance of
the coil, then you can match a resistance that will allow the maximum power
transfer to the resistors.  It will be hard since the arc resistance is in
between the two...  Maybe try 500 kohms and see what happens then...

Cheers,

Terry

At 11:23 AM 2/20/2001 -0800, you wrote:
>Hi All,
>
>The result of following experiment,fellow coiler
>conducted  recently,seems bit strange (at least for me
>,since I suggested him to do it estimation vise).
>
>According to the instructions, he hung ,verticaly,
>above 10" spherical terminal of his coil several
>resistors and grounded them via wire in a celling.
>Between  sharp point on the top of the sphere and
>string of resistors there was formed variable gap that
>way.
>For the particular coil and power level used,it was
>found to be most convenient to use 19" gap spacing.
>At this stage ,attached arc would be quite stable and
>could last for quite a time without deattachment.
>The string of resistors was made of identical parts-
>each resistor rated 5 W-1500 ohms.
>
>Now,the strange part.
>Experimentally,by low frequency test,it was found that
>,if forced to dissipate 10 W ,these resistors
>considerably  get warm.
>Since ,there were 9 of them put in series,90 W would
>do a nice heating effect to them (very soon).
>But,nothing of the expected heating was noticed.
>The experimenter,after few minutes of TC run turned
>the power off,and touched the resistors.
>They stayed reasonably cool.
>
>Used input power level for that and other experiments
>was always the same -about 650 W.
>This is a nice classical TC system;with 300 BPS
>rotary,20"*6" closewound secondary and by using 650 W
>it can occasionally  develop 36" point to point arcs.
>19" spacing provided for the arc the most stable
>condition with  the dimmest primary gap light running,
>though.
>The result of all said :Total string resistance
>9*1500=
>13500 ohm consumed less power than secondary power
>arc.
>This is very much in confrontation with usual view of
>the impedance ballpark of such arc.
>Anybody else performed similar expertiments,and
>wondered why there wasn't any smoke where it had to
>be?
>Any comments ,and thoughts on this would be welcome.
>
>
>Regards,
>Boris
>
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