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



Scott, you nailed it again!

http://www.youtube.com/watch?v=AUQeDqUhI3g

I used 6" aluminum ducting to toss another topload on top of my existing.  Another dramatic improvement!

Thanks again,
JJ


________________________________
 From: Scott Bogard <sdbogard@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> 
Sent: Thursday, August 8, 2013 5:51 AM
Subject: Re: [TCML] 5.25" SRSG tesla coil suggestions on improving performance
 

Also JJ,
     After actually watching your video I believe your toroid is way to
small for really long sparks.  The rule of thumb I like to use is toroid C
in pF is roughly = to toroid overall diameter in in. (believe it or not it
is actually really close).  Given that I found for single long sparks the
best toroid C can be found using this formula [C=0.9* (SQRT[P in watts of
the system]).  For a multi streamered system like you have one should
design for 0.5(SQRT[P]) Not sure why this formula works, it just does.  So
assuming 1 kW power you want a roughly 28 inch diameter top load, or two
smaller top loads yielding 28 pF of capacitance for longest streamers.
Credit where it is due I believe John Freu came up with this formula, I
simply realized later that they matched up with my own results very well.
Resizing your top load should help, but again I think matching your power
draw to your system with a higher break rate will yield more dramatic
improvement...  Remember "tuning" isn't just matching resonate frequencies,
it is also designing your system so power draw will be optimally utilized,
and losses minimized, this was always my biggest mistake as a beginning
coiler, impedance matching issues...

Scott Bogard.


On Mon, Aug 5, 2013 at 9:59 PM, JJ Dasher <redrum0381@xxxxxxxxx> 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
>
>
> 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.
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
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