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[TCML] SISG success
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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