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Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Before I start construction of a SGTC powered by a 70 Watt ignition coil power supply (J.Freau estimate of 14 inch arcs possible) I'd like opinions on the following options;
(A) 10nF 15kV MMC, 1.125J max gives about 62 bps (bangs per second) (B) 3.5nF 20kV MMC, 0.7J max gives about 100 bps
(X) 6 inch dia x 28 inch high 72 kHz secondary (Y) 3 inch dia x 12 inch high 250 kHz secondary
Which combination would you expect to give the longest arcs? (A) + (X) 221 Ohm (A) + (Y) 64 Ohm (B) + (X) 632 Ohm (B) + (Y) 182 Ohm
The approx primary impedance may be significant so I added it for comparison Please give reasoning. Thanks
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Definitely smaller secondary and bigger cap, the big one should be saved for some multi-kilowatt DRSSTC or SGTC
I also think you should put some more power in that IG, toacheive something around 100bps.
In flyback-mode, ignition coils operating on low frequency generate theri high voltage spike only in one 'direction' so your coil will fire only during that half-periode and 'sleep' in other.
This means you need to assure your iG works at exactly the same frequency as bps, otherwise long period of 'wait' will let the streamers to cool down and you'l probably be wasting power if you have more than one bang in one IG 'cycle'.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Marko, The ignition coil is operating at around 900 Hz with a hv diode to charge the primary capacitor that's about 9 charging pulses per discharge I'm limited to about 70 Watts output due to the mains transformer of the low voltage supply
Steve, with the large resonator I have about 40 pF total capacitance (coil + topload) that should be about 200 kV peak for 10 nF/15 kV the little resonator may be around 350 kV
I was mainly wondering - is 60 pps fast enough for streamer growth?
In any of the above cases I think 14 inch streamers (optimistic?) would look more impressive from the smaller resonator - which is what I will try first due to your advice.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
60bps usually isn't considered high enough, something around 100 seems to be giving longest sparks for input power. You'l have either to sacrafice some bang energy or increase input power to get to it.
Oh, with diode, it's OK for charging at any BPS you want; i assumed it's charging directly aka AC charging.
I somehow doubt you'l really get 30cm+ sparks at first with just 70W; I've never seen such a small SGTC to be efficient like that (but, everything can be 'for first time )
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Ignition Coil powered SGTC opinions wanted
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