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Re: statur report



Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

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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