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Re: [TCML] SISG success
Congrats on your SISG! All you guys are getting your SISG's up and
running and that's SUPER! I am apparently on the lazy side. I looked at
your coil specs. Thanks for nomenclature of calc, meas., and rated. The
coil itself is interesting. I have not seen a decent Q coil using 27 awg
at 1360 turns before, yet this one is. Q is on the order of 280. As far
as ESR, any type of increased impedance can drop power (regardless of
I'm happy to report I am again working on my SISG (I took a detour for
some tssp measurement's, but decided last week to continue on [the
primary I was measuring was built for the SISG]).
I've installed the new primary. I have a half bridge configuration at
the moment, but I'm gearing towards a full bridge. I expect I will see
dismal sparks as I'm building for an SISG with half the C that most
SISG's use. Part of my reason is that I want to see for myself the
results of low C (and work with it before I increase it). I will be
running 64nF. I guess I will see when I get the remaining bridge
finished (the only thing the coils waiting on at this point). BTW, I'm
using 6 boards for this which throws a wrench into the gears [a wee bit].
You mentioned the sparks decreased when you lowered the firing voltage
which would increase bps. My plans are to charge 3x higher in voltage
that your currently running which will require some time to get there.
What I'm considering is front end current limiting, to distinguish bps
regardless of cap size. It will always fire at the same voltage
regardless, but how fast it achieves that voltage (in my control) will
determine switching (bps). Yet, I'll be happy just to see it spark at
this stage in the game.
Thanks for your SISG update. It really helps those of us in the middle
of things to hear of successes such as yours. Unfortunately, it's a new
candle. So no thoughts on how to attain Terry's 42" sparks.
Herwig Roscher wrote:
Yesterday I have maxed out my copy of Terrys wonderful Piranha
(c) = calculated (m) = measured (r) = rated
No_load_output of MOT = 3367 V peak (m), MOT gets warm only a little
Firing voltage of 2 boards SISG4 set to 6900 V (r), IGBTs remain
stone cold even without cooling fan and even at max current.
Primary coil: inverted cone type, 25 deg (laying around), minimum
horizontal distance between primary and secondary coil is 1.26"
Lp = 13.7 µH (c)
Cp = 162.5 nF +- 5% (r)
Secondary coil: 6.3" by 22.8", 1360 turns, wire about AWG 27,
lowermost turns of primary and secondary coil are in the same plane,
F res = 106.5 kHz (m) when sitting inside the primary coil
Ls = 73,5 mH (c)
Cs = 10.6 pF (c)
Toroid 4.33" by 19.3" (outer dimensions) dryer duct (laying around),
covered with aluminum foil, vertical distance between toroid and
uppermost turn of secondary coil is 3.75"
C top = 20.7 pF (c)
I have increased Cp step by step , carefully retuning the system
after each step of course. Finally I reached a strike distance of
35.5". Although I am very satisfied with this good running system, I
would like to come a bit closer to the magic 42", Terry has reported:
The toroid is smooth (not so smooth as a spun one) and maybe a little
too small, but as it generates *one* streamer mostly, I assume it to
be close to optimal.
The streamer length *decreased* when I lowered the firing voltage of
the SISG4s to 6600 V = increasing BPS.
As the SISG4s continued regular firing when I increased Cp, the MOT
seems to be able to charge the 162.5 nF Cp up to full voltage.
As the calculated(!) peak current is close to 750 A already I did not
dare to increase Cp further more. Cp consists of several groups of
capacitors which are connected with thick but long wires. Some of the
capacitors are removed from a Klystron-power supply and get warm a
little bit. Could ESR and wire resistance be responsible for a lower
primary peak current, lowering the strike distance? Are there any
other measures I could try in order to increase the strike distance a
While copying Terrys Piranha system I have learned a lot and running
it is great pleasure. Thank you for inventing it, Terry!
Greed is the root of all evil !
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