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Re: [TCML] SISG success

Hello Herwig,

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 the component).

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.

Take care,

Herwig Roscher wrote:
Hi coilers,

Yesterday I have maxed out my copy of Terrys wonderful Piranha system:
(c) = calculated	(m) = measured		(r) = rated

No_load_output of MOT = 3367 V peak (m), MOT gets warm only a little bit.

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 little bit?

While copying Terrys Piranha system I have learned a lot and running it is great pleasure. Thank you for inventing it, Terry!

Bye		Herwig

Greed is the root of all evil !

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