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



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.
>> ______________________________**_________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxx
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>>
>
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>
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