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Re: [TCML] 5.25" SRSG tesla coil suggestions on improving performance



JJ,
     Please do switch to ASYNC, I absolutely guarantee performance will
improve, as you can use a smaller normal sized cap, and use a high break
rate to transfer all the energy you want.  I've been using two MOTs
unballasted for a while, it is a good system, but for low break rates I
suspect all your energy is wasted as losses.  You'll still trip a breaker
occasionally if you don't use a ballast, but that energy will go to spark
growth instead of a spark gap space heater...  See my coil here,
http://www.youtube.com/watch?v=_301ZMR6H48

Scott Bogard.


On Tue, Aug 6, 2013 at 11:10 PM, JJ Dasher <redrum0381@xxxxxxxxx> wrote:

> Hi,
> So this evening I removed the PFC, and the performance did not change
> much.  Maybe slightly worse.  The phase did shift, and I had to re-adjust
> my motor.
> As for the tank cap, Teslamap actually suggests 470nf for 4.4kv @ 300ma,
> or 236nf @ 150ma for SRSG.
> Regardless, I shrank my MMC this evening from 188nf, to 131nf by removing
> a few strings.  Performance was significantly worse after retuning the
> primary to about 3-3.5 turns.
>
> Maybe I just need to switch to async since building a cap that size would
> be ridiculously expensive...
>
> What do you guys think about switching to async??
>
> Thanks for the info!
> -JJ
>
>
> ________________________________
>  From: Scott Bogard <sdbogard@xxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Tuesday, August 6, 2013 9:58 AM
> Subject: Re: [TCML] 5.25" SRSG tesla coil suggestions on improving
> performance
>
>
> JJ,
>      MOTs do not need ballasting when you use only 2.  With that said if
> you use a doubler that will likely no longer be true, I can't watch your
> video as I am at work but I'll do that when I get home to see what is going
> on.  Gut instincts having mastered the two MOT system, ditch the PFC, they
> are NOT helping you if you are only getting 36 inches of spark, they are
> hurting, your current draw should be low at that spark length.  Second,
> your BPS is to low being synchronous for that cap size.  I use a 80nF and
> 700-900 BPS and get close to 60 inches of spark (spark continually
> increases with BPS until that range) your capacitor is 2.25 times bigger
> than mine, so your BPS should be 2.25 times slower than mine, so in the
> 350-450 BPS range, which is not really possible with a SYNC gap.  You could
> quadruple your electrodes and get 480 BPS, which is close, but you might
> have unexpected problems doing 480 BPS sync.  My advise for a better fix is
> to get a properly sized tank cap if you insists on going sync, it is
> definitely the easiest fix, a quick and dirty calc suggests 460 nF, but
> that seems high, so I'd use Java TC and see what is the recommended SYNC
> gap cap size assuming 4kV and whatever wattage is reasonable (around 1.5 kW
> is reasonable, so a secondary current of 375 mA for your calcs).  You may
> wish to assume less current since MOTs have a little bit of current
> limiting, 250 is generally what we see in the field...
>
> Scott Bogard.
>
>
> On Tue, Aug 6, 2013 at 9:59 AM, w5als <w5als@xxxxxxxxx> wrote:
>
> > Hi
> >       First I am no expert at this, with that said looking at your
> > pictures the tuning does not look to be right at 2.25 turns
> > and I would think that MOT's would have to be ballasted to keep the
> > current down. I have never use mot's before
> > and may be totally wrong here. I hope some one else put there input in on
> > this. I did not crunch the number on
> > this for the tuning neither, I may be wrong but I think that may be a
> > problem to.
> > alton
> >
> >
> > On 8/5/2013 8:59 PM, JJ Dasher wrote:
> >
> >> Hi all,
> >> I'm new here.  Although I've built a few coils in my past, I still
> >> consider myself a newb coiler.  I've never been the type to do things
> >> mathematically perfect, and tend to wing it as I go along, which may be
> my
> >> downfall here.  For the past couple of years on and off, I've been
> working
> >> on a 5.25" SRSG coil to use in a Halloween display.  This is my largest
> >> coil so far.  You can see it in action here:
> >>
> >> http://www.youtube.com/watch?**v=2P3T5zuT9DI<
> http://www.youtube.com/watch?v=2P3T5zuT9DI>
> >>
> >>
> >> and pictures of the guts here:
> >>
> >> http://imgur.com/a/0jgxR
> >>
> >>
> >>
> >> I'd like to get some constructive criticism and advice on getting this
> >> running better.  This trips my 20amp breaker after about 10-15 seconds
> of
> >> running, so I figure about 2.2-2.6kw?  I'm currently getting 36"
> streamers,
> >> which I feel are somewhat weak.  They are purple, and not very bright.
> >> Specs:
> >>
> >> Large old powerstat variac salvaged from power equipment.  Not sure on
> >> exact specs, but I assume it should handle 30+amps with ease.  Wired for
> >> approx 150v boost.
> >>
> >> Dual MOT's (pulled from 1200w commercial MWs), currently unballasted.
> >>  130uf of PFC caps behind them.
> >> 180nf MMC cap built with 10 strings of 8x 942c20p15k-f's.  1m bleed
> >> resistors installed.
> >> SRSG is a 5" acrylic disc attached to a 1800rpm sync motor.  4 flying
> >> electrodes for 120bps.  Electrodes are 1/8" thoriated tungsten.  Phase
> is
> >> adjusted by twisting the motor in its mounts.
> >> Primary is 3/8 copper tubing, slightly conical.  Currently tuned at
> about
> >> 2.25" turns
> >> Secondary is 5.25" x 24" 22awg magnet wire with a couple of coats of
> poly.
> >> Topload is a spun aluminum 4.5"x18" toroid.
> >> All high current busses are 4awg stranded copper with large soldered
> lugs.
> >>
> >> The next improvement I plan is to upgrade to 1/4" tungsten electrodes.
> >>  The stationary electrodes currently glow red hot after about 5 seconds
> of
> >> running, so I added a fan.
> >> I'd love to get some bright long white snakes like I've seen from
> similar
> >> size coils.  Please advise!
> >>
> >> Thanks!
> >> JJ
> >>
> >> P.S.  There is normally a safety gap installed, It just wasn't in place
> >> when I took those pictures.
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> >>
> >
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