Re: [TCML] SRSG "sputter"

[Gary Lau <glau1024@xxxxxxxxx>]

Hi Joe,

There's no way that having the gap BPS being a sub-multiple of the resonant
frequency would affect anything.  When the SRSG phase is significantly out
of whack, the gap fails to fire at the end of a mains half-cycle because the
electrodes aren't aligned at the voltage peak.  So the voltage now begins to
charge in the opposite direction.  But contrary to intuition, this energy
isn't simply "lost".  In an L-C resonant circuit, the energy transfers
alternately between voltage in the cap and current in the inductor.  The L-C
circuit at this point is the cap, and the NST secondary winding, resonating
at or near 60Hz.  Yes, you have a Larger Than Resonant sized cap, but when
NST secondary currents flow through capacitive loads, we think that the
current limiting shunts saturate, and ferroresonance kicks in and strange
stuff happens, permitting at or near mains resonance.  Bottom line, the
energy isn't lost, but when the voltage reverses, then charges to the
opposite polarity, it will reach a FAR higher voltage than on the previous
half-cycle, enough to break down a safety gap or insufficient RSG
insulation.

As John said, it's not possible that the cap can carry a charge between
bangs.  Once a spark gap fires, it won't stop firing until pretty much all
of the energy has been dissipated.  This happens pretty fast, and the fact
that the electrodes are spinning quickly doesn't matter.

Now that your gap timing is in the ballpark, can you describe what happens
as you sweep the phase adjustment Variac through its range?

Regards, Gary Lau
MA, USA

On Sat, Jul 10, 2010 at 12:09 AM, Joe Mastroianni <joe@xxxxxxxxxxxxxx>wrote:

> 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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