RE: Suggestion on Power Supply?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>

See comments throughout post:

 > The two major remaining variables in my design are
 > selection of the power supply and spark gap.
 > I initially wanted two 15Kv/60mA NST's in parallel,
 > but decided that was not going to be enough current
 > to charge a .03uF tank capacitor.

Actually, the LTR sized capacitor for a 15kV/120mA is probably about 0.05uF
My first coil was a 15kV/60mA NST powered coil and I used a 0.0277uF
capacitor (LTR sized) with
my synchronous gap.  It worked extremely well.  In fact, I think you are
better off with a LTR sized
capacitor with NSTs than resonant sized.  You're much less likely to kill
the NST this way.


 >From my
 > calculations, I figured it would take at least
 > 15Kv/270mA to charge the capacitor in 8.3 ms.
 > (AC half cycle), which I think can only be handled
 > by a pole pig. (that's 4KVA) A PT just won't do
 > because it'd always be run over it's ratings.

My portable PT powered (3.5kW) tesla coil uses a 0.03uF capacitor with no
problems.  I get about 6-8 feet depending
on output power with it.

 > So, should I try and get 240VAC 5KVA pole pig or
 > reduce my capacitance to something smaller? (Which in
 > turn would affect the frequency, which would affect
 > the topload, amperage->spark gap etc...)

No need to reduce the capacitance.  If you are using an asyncrhonous gap,
you could get away with even a smaller capacitor
with a potential transformer.  Perhaps even down to 0.01uF.



 > Also, I would like to run the coil with one of my
 > 15KV/60 NST's -- or even smaller, as a method for
 > low power tuning and adjusting. Then, switch a few
 > cables around and run it at whatever it wants :)
 > (270mA...) Does anyone do this, surely you don't
 > go full blast from the start...

The 0.03uF capacitor is perfect for a synchronous spark gap tesla coil using
a 15/60mA NST.

 > Next, I've got a bunch of 1/8" thoriated tungsten rods
 > left over from my first rotary spark gap. Are these
 > too small for the power levels involved now? I'm not
 > worried about them melting or anything like that, it's
 > just that 1/8" seems awful puny to carry 500 Amps.
 > I've seen SRSG's made with them before, but I would
 > think their "on" resistance is high...why have a large
 > capacitor when it's energy is going to be choked by a
 > high resistance gap?
 >
 > Would 1/4" tungsten be better?

Yes.  My 1/8" tungsten rods for my 3.5kW really take some abuse.  You need
some bigger rods for the higher powers.
Either that, or a some big cooling fans etc...

The Captain