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Re: Capacitor C/Peek



>>From bert.hickman-at-aquila-dot-comFri Oct 25 21:59:07 1996
>Date: Fri, 25 Oct 1996 13:20:22 -0700
>From: Bert Hickman <bert.hickman-at-aquila-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: Capacitor C/Peek

>Tesla List wrote:
>> 
>> >From rwstephens-at-ptbo.igs-dot-netThu Oct 24 22:57:34 1996
>> Date: Fri, 25 Oct 1996 00:37:12 -0500
>> From: "Robert W. Stephens" <rwstephens-at-ptbo.igs-dot-net>
>> To: tesla-at-pupman-dot-com
>> Subject: Re: Capacitor C/Peek
> 

><SNIP>

>> Now take a 12000 volt RMS xfmer and charge a 0.125 mfd cap to 16968
>> volts.  That's 17.99 Joules.  Bang this in 5 microseconds and your
>> sinewave peak power is 5.088 megawatts!  That's approximately the
>> spec of R. Hull's Nemesis coil and exactly those of my MTC system. My
>> first half sinewave is 6.25 microseconds though (80 kHz), so my theoretical
>> peak power is lower at merely 4.07 megawatts, and then taking K=0.2 and gap
>> losses into account I'm down to maybe 15% of that (a measely 610 kilowatts)
>> out the top?
>> 
>> I realize that the above is fast and simplified 'figurin' which
>> ignores a lotta stuff so flames are welcomed if I'm out more than 10 db. : )
>> 
>> rwstephens

>Robert,
>
>Your post got me thinkin' about coil efficiencies again...
>
>What if we look at this from a slightly little different light: How much
>energy
>do I start out with in the primary, and how much do I end up with in
>the secondary after I've transferred all the energy I could from the
>primary. The ratio of output vs input energy (transfer efficiency/bang) 
>could be a meaningful way of measuring how well a coil could perform. It
>should be measurable with either a 2-coil TC or a magnifying TC.  
>
>Assume you've done "single bang" measurements, and are able to farily
>repeatably set your primary gap breakdown voltage via a static gap.
>Also, assume you've
>estimated your peak secondary voltage indirectly (via low duty cycle
>sparklength or via calibrated pickup plate/storage scope). Assume your
>resonator is high Q, and is heavily capacitively-loaded so that
>virtually ALL of the resonator's energy will be stored in the toroid's
>capacitance at the point of peak secondary voltage. [Since most of the
>secondary's self- capacitance is concentrated towards the bottom, we'll
>choose to ignore it in this analysis - this only makes our analysis a
>little bit more pessimistic]. 
>Finally, lets assume that we quench the gap at the end of the first
>beat.
>
>We can compute the ratio of maximum secondary output energy versus
>initial input energy per bang:
> 
>   Ep = Initial energy = 0.5CpVgap^2
>   Es = Max Sec Energy = 0.5CtVsec^2
>
>The Energy Transfer Ratio = Es/Ep per bang
>
>Plugging in some specific parameters for my coil:
>My "single shot" low duty cycle output spark length is about 20", which
>I estimate to be about 400,000 volts, The toroid capacitance is about 26
>pF. My
>primary gaps are set for about 19 KV, with a primary tank capacitance of
>0.0205 uF. The previously measured primary Q was about 11 with the gap
>firing (no secondary), so my primary performance seems typical enough. 
>Plugging in these values I get:
>
>   Ep = 3.7 Joules
>   Es = 2.1 Joules  
> 
>   Es/Ep =  56% (!)  (per-bang)
>
>This is a much better than 15%...  No flames today Robert, you're
>certainly within 10 db   :^) 
>
>Now, I realize that I've made LOTS of assumptions above. Once we get
>breakout, the secondary output voltage and Q will both decrease.
>However, its not clear that these changes would cause a dramatic
>fall-off in transfer efficiency from the single-shot case. In fact,
>after breakout, when the secondary Q drops to a level closer to the
>primary Q, the energy tranfer efficiency might actually improve! 
>
>- Am I all wet?
>
>- What do you get when you plug in _your_ coil's parameters?  
>
>As usual, throw any extra Joules my way...
>
>Safe, and maybe even higher power, coilin' to ya!
>
>-- Bert --


Bert,

I think that calculating the power on the primary side, and then 
working the output power on the secondary by 1/2 [C(V^2)] on the 
topload capacitance and then getting an efficiency of conversion 
where the 'twains meet' is an interesting simplistic way to compare 
systems.  Unfortunately I have no firm number for the capacitance of 
the topload on MTC or the length of a single shot breakaway streamer, 
and therefore the discharge clamp limiting voltage value for my 
topload.  These are measurements I hope to conduct at the new lab.

BTW, you used 20 kV/inch for your voltage guestimation.  According to 
the famous paper by Clark and Ryan the value is more like 48-52 
kV/inch between sphere gaps. Trouble is, all sorts of factors 
influence this measurement to make it almost meaningless in the field 
(pun intended!).   Carefully controlled conditions must be set up to hope for
any accuracy when attempting to measure voltages by spark length.  I have plans
to build a directly connectable HV capacitive divider probe this year 
for the lab with a capability of at least 500 kV with accurate 
frequency response for waveform analysis.  This will be a very useful 
instrument with which many questions might be answered.

BTW, I pulled some numbers out of thin air for MTC (1.2 megavolt 
breakaway [60 inches -at- 20 kV/inch] and 50 pF topload) and got a really big 
output Joules which was about double my input power.  I've got to go 
write a post now which will give me instant celebrity status over at 
the free energy camp.

Thank's for your input, as always.

regards,
rwstephens