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Re: [TCML] Notes on first SRSG...
Hi Joe,
I also run a 15/60 with an SRSG. My SRSG is documented at
http://www.laushaus.com/tesla/sync_gap.htm
Running with a static gap and a cap sized for an SRSG will be problematic.
The firing will be eratic and draw huge mains currents - it just won't
work. But I'm surprised that you were unable to get the gap to fire at
all. Are you certain that the gap spacing wasn't dangerously wide?
With the SRSG and appropriate cap, the phase is very critical, and manually
setting the phase will be difficult, so I'm glad to hear you sprung for the
Freau phase adjuster. Are you sure that that is working well with an
adequate adjustment range? I tested mine by taping a small magnet to the
RSG motor shaft and scoping the voltage from a pickup coil, with the scope
line-sync'ed. You want at least 3msec of adjustment latitude.
I don't recommend running the coil without a load. When I was
experimenting, I saw the need to play with the phase without having to worry
about secondary sparks, so I replaced the PRIMARY coil with a dummy load - a
bank of three series connected 120V/500W halogen bulbs. The photo in the
web page referenced above shows two series bulbs just loosly wired, but I
subsequently saw the need to make a purpose-build fixture to hold the 3
bulbs that won't flop around.
Using the dummy load, just play with the phase and tune for maximum
brightness.
You mentioned that you ran the SRSG with the 18nF cap. If you use a cap
that's too small, there is a high risk of the bang voltage being too high,
and it may damage the NST. Do you have a correctly set safety gap in
parallel with the SRSG? I can't overemphasize how important it is to have a
safety gap always in parallel with a rotary gap.
Note that changing the cap value or Variac setting will result in a
different optimal phase setting. The Variac variation can be compensated
for by using the Freau phase adjuster, but I worry that such a different cap
size will need a very different phase setting that the adjuster can't
compensate for. You really should just use the right cap size (28nF or
more) and stick with that.
In practice, when I run my coil, I use the phase adjuster Variac as the main
"throttle". With the phase adjusted too early, I can turn the power Variac
all the way to 120% and the SRSG will fire at a very small bang size. Then
I advance the phase and the bangs get larger and larger, until the safety
gap fires. Then I back off just a tad and that's the sweet spot.
Regards, Gary Lau
MA, USA
On Sat, Jul 3, 2010 at 11:02 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:
> HI All,
> I got my first SRSG running today. Some notes, and maybe you experienced
> fellows can enlighten me on the phenomena I'm observing --
>
> - Running a 15/60 NST. 17 turns of 1/4" x 1/4" refrigeration line as
> primary. 22" tall, 30GA, 4" dia secondary. 25nf MMC (3 banks of 18
> 0.15mf by 2kV). Tophat is an 18" x 4.5" spun toroid. Using 2 variacs -
> one in John Freau's phase-shift configuration, and one for primary power.
>
> - Experimented running with the static gap and 25nf, instead of 18nf on
> the MMC. With 25nf on the MMC the variac has to be an nearly 120V for the
> static gap to fire. It's kind of all or nothing. Turning on the primary
> is around the 13th turn in this configuration
>
> - Switched to the rotary gap - difficult to "tune" the SRSG phase in this
> configuration, because you either get it to fire, or not, with max power on
> the power variac. Lots of trial and error.
>
> - Tried tuning the phase without the coil resonator connected to the SRSG.
> Sort of works...think I got it firing right.
>
> - Took the 3rd bank of the MMC off - and lowered the total tank cap to
> 18nf. Now the gap fires at lower voltages, and I can tune the phase.
> Though now I'm worried I should switch back to the 25nf capacitance to avoid
> blowing something.
>
> With 18nf capacitance and the SRSG rotating in what I think is a reasonable
> sync phase with utility power - I'm getting some really great results.
> Sparks are bright and "mean" sounding - full of what I presume to be 60hz
> buzz.
>
> Is there any reliable way to tune the phase of the SRSG with a scope (or
> without) - without having to rig up some kind of optical strobe sensor?
>
> Thanks to all for the help!
>
> Joe_______________________________________________
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> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
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