Re: FW: 15/120 NST Coil Static Gap Performance Problems

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Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Ian,

At 07:15 AM 2/16/2004, you wrote:
>Hi all,
>
>I having a difficult time trying to understand this problem, so it's going
>to take a bit to explain, so sorry all in advance for the long post :) :)
>
>Tuned my 6" coil last Saturday afternoon with the help of Claude.  I don't
>have a decent static gap, so Claude kindly brought along his sucker gap,
>control box which has a current meter, and an extra variac to help tune the
>SRSG and to control the suction to the suction gap - BTW: thanks for
>Saturday Claude :-)
>
>Firstly, we got some good streamers on Saturday :)  Especially with my SRSG
>and the 62.5nF tank cap.  Some nice bright power arcs to the colourbond
>roofing and overhead metal pipe.  Some out to 5 foot.  One power arc to
>ground, through a vice mounted on my workbench.  The 5 footers at the end of
>the day, when both Claude and I think we just about got it right, wanted to
>go further.  A couple of streamers arced through a metal jerry can on a
>shelf, through the half inch thick wooden shelf above it (directly through,
>it was no barrier at all) and upwards to the furthest point on the corner of
>the ceiling 5 foot away - so I am getting very close now to predicted
>output.  It was definately limited by the roofing.  I am now getting
>prepared for an early evening full power outdoor test.

So I take it you have a 15/120NST or the equivalant, 100Hz.  LTR values are 
38.2 (static) and 66.4nF (sync).


>I learnt a few things on the day.  Don't use GTO-15 for tank cable -
>dramatic drop in output.  This was the first thing changed, for some thick
>multi-strand copper cable, and the output instantly improved.  This was
>unshielded - so I am going to get some even thicker copper multi-strand and
>shield it myself.  I learnt not to let this unshielded copper touch the
>varnished wood of the primary base (it caught on fire :-0).

Cables can also add primary inductance and change the tuning.  They have to 
be very low loss or they will dramatically rob the system of power.


>And now the mystery.  My coil didn't respond too well to the sucker gap.
>Streamers about 4 foot max.  But that's not the mystery.  No matter the
>tuning, tweaking, adjusting of coil coupling, gap size,  cap size (LTR
>static -at- 37.5nF or LTR rotary -at- 62.5nF, or sucker suction velocity, the
>output did not improve beyond this, and the gap seemed to sputter, and
>seemed to be at a low break rate (slower than SRSG at 100bps, you could
>easily tell the difference between the two).  Now neither Claude nor I could
>understand the reason for this, so if anyone can shed some light as to why
>????

Hmmm... Everything sounds right to me.  Might be a problem with the sucker gap.

>  Is my 15/120 NST bank not getting the caps charged enough ?  Current
>draw with sucker gap was 15A average, tuned, from 240VAC mains (Australian
>supply).  With SRSG, tuned, that dropped to about 10A average.  This sucker
>gap performs much better on it's owner's (Claude's) coil.  On his coil, it
>roars like a chainsaw on heat, and the gap spark is much brighter.  On my
>coil, it is loud, but not as loud, and the spark brightness is sputtery and
>not quite as intense (although still very very bright).

The static gap LTR coil will indeed have less performance than a sync 
rotary coil.  look at the input power:

P = BPS x 1/2 x C x V^2

Psuckergap = 100 x 1/2 x 37.5nF x 21000^2  ==  827 watts

Psrsg = 100 x 1/2 x 62.5nF x 21000^2  ==  1378 watts

Your SRSG setup has 67% more power to start with!!  Your power factors are 
low (0.38 and 0.34) but that is probably normal.  The real key is that your 
SRSG system has a 67% larger cap and thus 67% more power.  The streamer 
length should be 30% greater with the SRSG.


>My coil instantly performed well on the SRSG, once tuning and SRSG alignment
>had been tweaked.  5 footers wanting to be longer.  Nice bright power arcs.
>Clean 100bps break rate.  Very loud but even sounding.  Very smooth.  I like
>the way the streamers seem to "snake out" of the toroid, and fork more, on
>the SRSG.  Noticed this on Claudes coil as well.  Even breakout over the top
>toroid, with some arcs and streamers moving around the toroid.
>
>Wish I could have taken pictures.  My sister will be at my place on
>Wednesday, with her digital camera, so I'll do an outdoor SRSG run in the
>early evening and get her to take some pictures of it all for me :)  Hoping
>for 6 footers.  Wish me luck :-)  I'll get some photo's up on a Web page
>somewhere.
>
>Any help with the sucker gap performance problems would be greatly
>appreciated.  I want to build one.  I like the more random and thicker,
>brushier output (albiet shorter) it gives as well.

Thus is why people like sync gap LTR systems due to the greater power 
throughput.  Maybe someone has a way to sync trigger the sucker gap?

Cheers,

         Terry


>Rgs
>Ian