Re: [TCML] SRSG "sputter"

[futuret@xxxxxxx]

Joe,

Good to hear you found the better phase setting for the rotary.
The sputter setting may have been the notorious "reversal firing
mode", which draws excessive current and can cause NST damage.
Seems the voltage swings in one direction then the other before
firing in this mode.  With some NST/cap value combos, both
modes (reversal and regular) give similar spark lengths.  The reversal
mode has not been thoroughly explored yet as far as I know, but 
I did do various tests.  Depending on the setting of the safety gaps, 
they will either fire first during the first voltage swing, or the rotary will
fire after the reversal.

The 120kHz won't cause any 120 bps problems because each firing
of the gap is an independent event.  Energy doesn't carry over from
bang to bang*.  It's not like CW (continuous wave operation) where
you get voltage build up limited by Q of the system.  Although Q is
still a factor from a loss perspective at least (mostly) before spark breakout.

*Although energy doesn't carry over from bang to bang, the ionized
spark trails from the toroid do stay hot in the air, and allow the sparks
to grow longer bang to bang (up to a point).  So in that sense the energy
*does* carry over from bang to bang... but not in the Tesla coil... it happens
in the air.

John
 

-----Original Message-----
From: Joe Mastroianni <joe@xxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sat, Jul 10, 2010 12:09 am
Subject: Re: [TCML] SRSG "sputter"


Hi All,

Well, indeed the problem was curable by advancing the timing on the rotor about 

30 degrees.  Now I can bring it up to full power - BUT - I would say that on 

full power the arcs aren't as large as they were when I had the "sputter" 

problem.  After doing a bit of reading I've come to the conclusion that the 

sputter was indeed some off-timing resonance issue where I was not entirely 

discharging my MMC bank.   Perhaps it was some out-of-control ringup issue that 

the safeties were saving me from, with the pulses hitting the cap bank at some 

multiple of the resonant frequency.  I measured my  Thus the safeties were 

firing to offload the additional charge.



Java TC suggests my resonant freq is around 130khz but it wouldn't surprise me 

if it was closer to 120khz, which, perhaps, would cause some issues at 120bps 

under certain conditions.  It would take me going out and getting some HV probes 

for my scope to see it for myself...



Meanwhile, it works now fine.  

Of course, this will not stop me from trying the other SRSG designs.  I'm too 

curious.

I'm also going to try an ARSG, as I do like the sound.... ;-)



Joe



 
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