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Re: statur report

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 05:17 PM 12/27/2005, Tesla list wrote:

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!
Which raises a big stored energy safety problem! The rule of thumb is that you want 5-10 times the energy stored that you will dissipate in a half cycle. So, if you're running a 5kVA system, in 1/100th of second, you're dissipating 50 Joules, so you need to store 500 Joules or so. That will make a fairly good sized bang.
There's also the whole capacitor input filter problem. The line current will be drawn in big peaks. 


A choke input filter might be a good idea.
An even better idea is to run off 3phase so that you don't need as much energy storage in the filter.
I've contemplated that it might be better off to synthesize 3 phase on the lowvoltage line side and then do away with the filtering (use a small choke for resonant charging). You already have to muck around with the primary side so you can control the current and voltage, so why not do some sort of capacitive or rotary converter scheme to make 3 phase.
You'll still wind up storing the energy, but at least you're storing it in a form that's easier to manage (i.e. the rotational energy in the rotor of the converter, or in relatively low voltage capacitors at AC line voltage). 




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
A DC system could allow a lot of interesting ideas.. such as running multiple coils at multiple break rates (the "Tesla Coil Organ" idea)
Once you've solved the engineering challenge of providing a reasonably stiff DC supply at 20kV at 1 amp, you've got a lot of interesting stuff you can do.