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Re: statur report



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>



The standard "rule-of-thumb" is the filter cap should be 10 x the tank resonant value cap for a DC charging system. This works excellent in most all cases.

Dr. Resonance



Hi Robert,

Yes, you seem to have gone DC without an absolutley
HUGE filter cap (2 uFd) but you still pretty much make
my point, as 2 uFd is still 20x larger than .1 uFd and 2
uFd at 22 kV makes for 484 J. That's still a very lethal
level of stored energy to have to worry about properly
bleeding off after powering the coil down. I am surprised
that you are able to get by with only 15 turns of house
wiring around a 1" diameter X 6" long form for your choke
though. BTW, what size is your DC system?

David Rieben

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, December 28, 2005 1:28 PM
Subject: Re: statur report


Original poster: robert heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>

David : I have DC TC coils with 1/2 wave rectifiers and small filters of
only 2 MFD. A shohe coil is esential but it may be small inductance. I use
15 Turns of house wire 1 in diameter and 6 in long air core. The inductance
is low but it works. The large size is for insulation at 22Kv to prevent
turn to turn arcing.
     Robert   H
--


> From: "Tesla list" <tesla@xxxxxxxxxx>
> Date: Tue, 27 Dec 2005 18:17:46 -0700
> To: tesla@xxxxxxxxxx
> Subject: Re: statur report
> Resent-From: tesla@xxxxxxxxxx
> Resent-Date: Tue, 27 Dec 2005 18:14:20 -0700 (MST)
>
> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> Justin,
>
> To build a DC Tesla system "right", you are going to need
> some really BIG filter capacitors! I'm talking like quarter
> shrinker/can crusher sized caps! Then of course you'll al-
> so need to make sure that you have an adequate inductive
> reactor to keep all of the filter cap(s)' energy from trying to
> flood the spark gap and damaging or destroying the other
> tank circuit components. 0.1 uFd isn't nearly enough capacitance
> for a FILTER cap for even a small DC resonant Tesla coil sys-
> tem. Think 10's of uFds. Others that aren't as numerically
> challenged as myself can run the numbers and formulae for
> you.
>
> Having said all of that, it should be quite apparent that a
> typical AC Tesla system is considerably simpler to build and
> you get about the same performance per input power, so
> why bother with the extra labor, time and co$t of building
> a DC system unless you just want to meet the challenge?
>
> David
>
> ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Tuesday, December 27, 2005 1:18 PM
> Subject: statur report
>
>
>> Original poster: Just Justin <rocketfuel@xxxxxxxxxxxxx>
>>
>> Greetings,
>>
>> After a long period of research, I've finally started building my
>> first coil.  I must say, I was inspired by Malcolm's speed and so
>> I've set my sights on having something to show my friends on New
>> Year's Eve.  It will go well with the fireworks and flamethrowers.
>>
>> Anyway, my first source of good information was Richie Burnett's
>> wonderful site, which made me want to go straight for a DC
>> resonant system right away.  After thinking it over, I decided
>> that going DC resonant with my 12KV NST would require a very
>> high voltage tank cap and that I'd be better off using MOTs due
>> to their lower voltages.  In the meantime, I thought I'd try a
>> NST-bridge-filter caps DC system.  I built a propeller gap but
>> have had some alignment issues due to the way I constructed the
>> rotor, so I've shelved that and made a 6-segment (1"x6") copper
>> tube fan-blown gap.  Now if you're still reading I'm sure you're
>> probably going to say that there's no point in DC with the static
>> gap and I'm mostly convinced myself.
>>
>> However, when constructing the fan blown gap, I observed it as
>> NST + bridge, and again as NST + bridge + filter caps and saw very
>> different sparks.  Without the filter caps, the gap frequency was
>> very high, and the sparks were purple-orange, and they seemed to
>> persist as the fan blew them to the far side of the pipe.  With
>> the filter caps (0.1 uF) in place, the gap fired much less frequently
>> and the sparks were white and seemed "hotter".
>>
>> Of course this had me scratching my head.  My current theory is that
>> with AC and a static gap, the gap might break down several times >> during
>> the portion of the AC wave that is of a higher voltage than the gap
>> can withstand before breaking down.  With the NST + bridge only, this
>> would be more or less the same situation, but without the
reversing polarity.
>> With the addition of the filter caps though, I imagine that the filter
>> caps take a wee bit of time to 'fill' to the threshold voltage of the
>> gap, and when they do discharge, they add to the NST's current,
leaving >> the
>> cap's voltage after the spark somewhere between 0 and the gap
>> threshold voltage.
>> Once the plasma has been created, resistance goes down and so
I'd >> imagine
>> they are somewhat depleted after the spark.  Then the cycle repeats.
>> I guess the question is how long does it take the filter caps to >> charge
>> to the gap voltage and is that longer than 1/120th of a second?
>>
>> My assumption is that any energy I might be storing in the filter caps
>> is just going to drain out through the spark gap, and therefore is
>> pretty much useless without the accompanying charging reactor and D-Q
>> diode of a full DC resonant charging system.  I still don't entirely
>> understand why the filter caps would not discharge through the spark
>> gap in a resonant system, except that possibly the charging reactor
>> limits the current out of the filter caps.
>>
>> I have a few specific questions that I'll post in seperate emails.
>> Thanks for reading and I'll appreciate any comments y'all might have
>> to offer.
>>
>>
>> Justin in Austin
>>
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