Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
Hi Bart.
I'm glad to finally have this thing up and running.
With very little tuning and much tweaking to go, I hit
7' on my second day, at 200 volts and around 25 amps.
I've been working on this thing since 2003! I ran it
once two Halloweens ago, but had a gap meltdown:
http://www.hot-streamer.com/adam/bigass_coil/Meltdown.jpg
I not only melted pvc, but solder as well.
When I first started modeling this coil with either
JavaTC or FanTC, I seem to recall a minor upgrade was
requird, as my coil was a little outside the norm as
far as aspect ratio. But you got it fixed and it
pretty much nailed my tuning points.
I occasionally hear my welder thumping, but never
noticed my pig doing so.
Here's my rsg, before I mounted the motor I got from
you:
http://www.hot-streamer.com/adam/bigass_coil/srsg.jpg
It's a 3,600 rpm 480 bps TTR srsg seen here:
http://www.ttr.com/rotary_spark_gap.htm
It claims to be good for 15 kVA. I got it from David
Rieben. I tried running my coil srsg style, but
decided to go arsg. I originally ran the srsg motor
with one phase of the three phase vfd, and it kinda
worked, but the vfd wasn't real happy with the phase
imballance. So I bought your 3 phase motor and had the
hub line bored (no turning back now) and added the
1725 rpm motor.
http://www.hot-streamer.com/adam/bigass_coil/rsg1.jpg
http://www.hot-streamer.com/adam/bigass_coil/rsg2.jpg
Excuse the poor pics, as I just took them in a dark
garage with no flash or tripod. Since I've heard
several people state that they couldn't run their
rsg's with both sets in series, I set mine up to use
just one set. Maybe I sould try the other set in
series, though I'll have to cut down my motor mounts
to accomodate the larger motor.
As to the VFD, I have it setup with a pot which is
currently set for 45 - 150 Hz! It seems happiest (at
current power level) around 70 - 80 Hz. I'm curently
using five sets of two 37667's, so I have 75 nF. I'd
like to try removing 15 nF at a time, while adding Hz,
to see if adding more pri H helps my gap issues.
Here's my schematic:
http://www.hot-streamer.com/adam/bigass_coil/schematic.pdf
Adam
--- Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "Barton B. Anderson"
> <bartb@xxxxxxxxxxxxxxxx>
>
> Hi Adam,
>
> Glad to hear your getting the coil up and running
> with the VFD! I've
> read your posts at work but haven't had time at home
> or work to
> respond in the past few days. I originally used a
> resistor in my pig
> (2.5 ohm, really big 3KW resistor). My reason for
> using it was the
> pig would thump at high power levels. The change in
> current in the
> core causes the thumping and it is a very
> discernible audible low
> frequency noise. I only heard this with my 13"
> diameter coil, but
> quit using it with my smaller coils as the thumping
> was no longer
> there. I'm not sure this will help with your issues
> at the gap. The
> resistor is there to limit the speed of change of
> current in the core
> (slow the change down) as a fixed value. I don't
> realize a
> relationship for the gap issue. I mention this
> because it's probably
> wise to go down some other avenues first.
>
> I suspect the gap itself is the issue. I personally
> use as close a
> spacing as possible. I don't remember in the posts
> if you described
> your gap, but if not, that would maybe help (or
> picture would be
> cool!). I personally don't like a static gap in use
> with a rotary
> when I consider an ideal case. A static gap is a
> band aid for a
> rotary that needs to be beefed up for the power.
> But, due to cost and
> onhand components, it is often the best coarse of
> action for the time
> because as rotary requirements for power increase,
> the cost goes up.
>
> Anyway, I was just thinking if we could see your
> ARSG, than maybe
> something might stick out to those who have run into
> similar problems.
>
> Take care,
> Bart
>
> PS, are you adjusting speed with the 0-10V analog
> input or are you
> using presets? (just curious).
>
>
>
>
>
> Tesla list wrote:
>
> >Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
> >
> >Thanks. I just added another 30 Hz to my VDF setup,
> so
> >I can go from 30 to 150, with a 1725 RPM motor.
> That
> >will allow breakrates of up to 575. At current
> power
> >levels, I get better length at around 70 - 80 Hz,
> >which is around 280 bps. I started this coil back
> in
> >2003 if I recall. While I say I've played with gap
> >spacing some, I kinda concider this weekend to be
> >first light, as I was unable to get the rsg to
> "keep"
> >the spark, as my safety gaps always took over. I'll
> >keep playing and will look for a big resistor to
> use
> >in line with my welder. I'vwe always read about
> some
> >folks needing resistive ballast, but I thought that
> >was just to keep their welder happy. I have two
> slide
> >chokes that I plan on using instead of my welder.
> Do
> >they also need the resistive ballast, or is this
> more
> >of a welder ballast issue?
> >
> >Adam
> >
> >--- Tesla list <tesla@xxxxxxxxxx> wrote:
> >
> > > Original poster: FutureT@xxxxxxx
> > >
> > > In a message dated 3/25/07 8:53:32 PM Eastern
> > > Standard Time,
> > > tesla@xxxxxxxxxx writes:
> > >
> > > >Original poster: Yurtle Turtle
> <yurtle_t@xxxxxxxxx>
> > > >
> > > >I've noticed a number of large coils use arsg's
> > > with
> > > >no problems, while others seem to need a static
> gap
> > > in
> > > >series with their arsg. Mine seems to be the
> > > latter.
> > > >Does anyone know why some need this and others
> > > don't?
> > >
> > >
> > > Adam,
> > >
> > > This is an interesting question and I think it's
> > > affected by
> > > various factors. Factors such as coupling,
> > > ballasting,
> > > transformer voltage, cap value, power level,
> > > mechanical
> > > dwell time, rotary gap spacing, electrode speed,
> > > etc.,
> > > could affect this.
> > >
> > > With a high break rate, a small amount of
> ballasting
> > > is usually needed to obtain sufficient power
> > > throughput.
> > > This small amount of ballasting makes the gap
> appear
> > > more like a short to the transformer when the
> gap
> > > fires.
> > > The gap may try to power arc, or it may try to
> > > re-fire
> > > again while the electrodes are still aligned
> which
> > > will
> > > cause inefficient operation and heavy current
> draw.
> > > This especially true with a slow rotary speed
> and
> > > with
> > > wide diameter electrodes. This becomes even
> more
> > > true
> > > when the rotary is slowed down for lower break
> > > rates.
> > >
> > > Making the gap spacing wider could possibly stop
> > > some
> > > of the problems above and make the static series
> gap
> > > un-needed. With some coils, a very close gap
> > > spacing
> > > is needed to obtain steady firing. So
> > > experimentation
> > > has to be done to find the best spacing. In
> your
> > > case
> > > I see you tried various gap spacings, so some of
> the
> > > other
> > > factors above may be affecting your coil.
> > >
> > > Richard Hull used to use some resistive
> ballasting
> > > along
> > > with the inductive ballasting to dampen unwanted
> > > thumping
> > > and resonances in the power transformer at high
> > > break rates,
> > > with a small amount of inductive ballast.
> > >
> > > Coils with large caps running at 120 bps or so
> > > generally
> > > use larger amounts of inductive ballast, so they
> may
> > > have
> > > less need for a series static gap in series with
> the
> > > rotary.
> > >
> > > Regarding running 4 series rotary gaps, this
> also
> > > depends
> > > on many of the types of factors mentioned above,
> > > such
> > > as voltage, resonances, etc. I think Ed Wingate
> > > uses
> > > 0.020" spacing or so on his 12 point series
> rotary
> > > gap on
> > > his magnifier. If four rotary gaps are used,
> the
> > > spacing
> > > may need to be closer than when using 2 gaps.
> For
> > > my
> > > small coils such as the TT-42, I have to run the
> > > rotary gaps
> > > very close with just a few thousands of an inch
> > > spacing.
> > > That coil uses only two series rotary gaps.
> > >
> > > I remember Bob Svangren saying that one of his
> coils
> > > ran well with a rotary with 6 electrodes, but
> would
> > > not run
> > > well with 8 electrodes. I think it was because
> he
> > > had to
> > > slow the speed when using 8 electrodes, and it
> may
> > > have
> > > made the dwell time too long. This may have
> caused
> > > re-firing of the gap while the electrodes were
> still
> > > aligned
> > > (two firings per electrode presentation).
> > >
> > > John
> > >
> > >
> > > >My 10" coil used this gap:
> > > >
> > >
> >
>
>http://www.hot-streamer.com/adam/bigass_coil/srsg.jpg
> > > >
> > > >modified to use a 3 phase 1725 rpm motor for
> > > between
> > > >120 and 460 bps. I've tried various rsg gap
> > > spacings,
> > > >but adding a series static sucker gap makes it
> run
> > > >very smooth. Unfortunately, my coil is so loud,
> I
> > > have
> > > >to limit my runtimes to several hours a week.
> That
> > > >limits my ability to make modifications and try
> > > them
> > > >out, so I'm trying to leach info from folks who
> > > have
> > > >already figured this out.
> > > >
> > > >Has anyone had any luck running all four gaps
> in
> > > >series on an ASRG similar to mine?
> > > >How about two sets in parallel?
> > > >What gap spacing are most folks running on
> their
> > > ASRG?
> > > >For folks running a series static gap, what
> type,
> > > >number of gaps, and total spacing have you
> found
> > > work
> > > >best?
> > >
> > >
> > >
> > >
> > >
> > > **************************************
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> > >
> >
> >
> >
> >
>
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