Joe,
Are the rotary gaps set close enough together for reliable firing? If
the
electrode spacing
is too wide, the rotary will only fire at a high variac setting. Of
course
if the electrodes
are tungsten and are set too close they can crash and break off. In any
case
the coil should begin firing at a lower variac setting I would think.
25nf
should be
OK for a 15/60 NST. 25nf should not be too large to fire reliably.
The phase setting for the SRSG can only be set by adjusting for longest
sparks.
It cannot be adjusted using a scope because the firing timing depends on
the
exact characteristics of the NST and the cap value. The phase setting
should
not be set without the resonator in place. That can damage the caps and
won't
work anyway. You may be able to get in the general ballpark range using
a scope, but I didn't bother in my own work.
The phase controller gives only partial phase range. If you get best
results
at the end of the phase controller variac range, then you'll need to
rotate
the motor itself some in it's mounting cradle, or shift the rotor
relative
to the
motor shaft to get the proper range. Of course the phase setting will
be
very different for the 25nf cap and for the 18nf cap. This may be why
you
got better results with the 18nf cap (or part of the reason).
If you watch the rotary spinning under fluorescent light, you'll be able
to
see if it's truly running in sync (just the rotary alone, no Tesla coil
firing).
The light pattern will rotate if you lower the rotary voltage so it
drops
out
of sync, and you can hear the hunting sound when it's almost syncing
as you raise the voltage. (I'm referring to the motor voltage not the
phase shifter variac setting). You can just unplug the motor and you'll
see the light pattern start rotating, then freeze when you plug the
motor back in and it syncs. Some people have a very very very hard
time seeing these patterns under fluorescent light however.
(Maybe you did all these verifications tests already).
The sound of the system should be 120 BPS, not 60 BPS. You should
be getting 56" sparks or so if you're using a step up type variac
(140volts).
I'm surprised the variac has to be turned up so high for the static gaps
to fire. Maybe the static gaps are set too wide? I'm assuming you
have the coil tuned correctly at the primary tap. I didn't verify using
JAVA TC or anything. You'll probably need to tune outward by a turn
or two more than JAVA TC suggests, because JAVA TC doesn't
account for spark loading effects on the tune point.
John
-----Original Message-----
From: Joe Mastroianni <joe@xxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sat, Jul 3, 2010 11:02 pm
Subject: [TCML] Notes on first SRSG...
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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