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Re: Questions Questions

Subject: 
            Re: Questions Questions
       Date: 
            Wed, 26 Mar 1997 06:48:22 -0800
       From: 
            Bert Hickman <bert.hickman-at-aquila-dot-com>
Organization: 
            Stoneridge Engineering
         To: 
            Tesla List <tesla-at-pupman-dot-com>
 References: 
            1


Tesla List wrote:
> 
> Subject:
>         Questions Questions
>   Date:
>         Tue, 25 Mar 1997 00:06:10 -0500
>   From:
>         "George W. Ensley" <erc-at-coastalnet-dot-com>
>     To:
>         tesla-at-pupman-dot-com
> 
> Hello,
> I have been attempting to optimize my 6" coil with some success. What i
> have
> noticed is that the coupling coefficient seems to vary a good deal. Any
> number of factors seem to affect it, breakout, toroid height, toroid
> size,
> coil height, etc. I am using K=(Fh-Fl)/Fr to find K is this correct?
> 
> It has been interesting to note that while using a large toroid, 7"x 30"
> which was difficult to break out, the system exhibited all the signs of
> over
> coupling. When a small tab was added to assist breakout, all of the
> signs
> went away and the best spark to date was achieved.
> 
> Some how i get the feeling that the signal generator and the O-scope
> aren't
> telling me all i want to know. What is the k of the system while in
> operation? How can i check it?
> 
> -------------
> 
> The best thing that ever happened to my TC was when a fan failed and i
> melted down my RQ pvc gap. I was forced to build a new gap using a shop
> vac
> a plastic 5 gallon bucket and some 5/8 copper pipe. It's noisy but my
> sparks
> went from 48" to 67" with no other change.
> 
> I have observed a wave shape change in the output of the coil that is no
> doubt the results of better quenching. It is now a single hump with a
> fairly
> rapid rise and slower ring down. Previously a double hump was evident
> with
> the second being much smaller than the first but still causing the event
> to
> last almost twice as long.
> 
> I have been attempting to follow the discussion on optimal quenching but
> lack some basics. What was i seeing? Is that the beat notch or was it
> just
> the gap trying to fire again? How are these measurements made? What is
> the
> test setup?
> 
> ------------
> 
> I was pleased to see Richard Hull on The Learning Channel tonight with a
> big
> TC running in the background. Interesting stuff water.
> 
> George............


George,

Congratulations!! From the sounds of it, your new gap IS quenching at
the ideal point. Your secondary waveform in that case will rapidly rise
to the maximum, and then come bak down relatively slowly (dependent on
how "big" the streamers are). The added sparklength is due to keeping
more of the energy in the secondary rather than coupling a portion of it
back to the primary and losing it in the gap.  

Regarding coupling, now that you have a good quenching gap, you can try
increasing the coupling by raising the primary relative to the
secondary. The low-power measurements of Fh, Fl, and Fr above are a good
approximation. The trick now is to experimentally find the best point of
operation. Based upon your excellent results already, I'd recommend
changing the height by no more than 1/4" at a time. Each time, run the
coil in a dark room and look for any signs of overcoupling (usually
inter-turn flashovers) while slowly ramping up the power level to the
maximum. If you start seeing "Christmas tree" corona between the top of
the secondary winding and the strikerail below, lower the toroid a bit.
Adjusting "k" is a little tricky, since increasing the coupling also
makes the gap more difficult to quench, and once you start getting
"double humps" again, you may also start getting inter-turn flashovers.
For a fixed vacuum gap configuration, there's no way I'm aware of to
maximize "k" versus the the rest of your system other than trial and
error. 

Once you reach the point of overcoupling, back off a bit, and start
adjusting the tune a bit. Usually you'll need to increase the primary
inductance a bit from "instrument tune" until you get best performance.
Although this process may take a little time, you'll end up with a
system that's running at peak performance. 

After doing all this, NOW go back and do a low power remeasurement of
Fl, Fh, and Fr. With a little bit of luck, you'll be in the .18 to .23
range. Sounds like you already have a kick-butt coil, but this will
wring the best out of it. BTW, what are the other parameters of your
system (input power, tank cap/primary size, and secondary /toroid
size?). Again, congratulations - job well done!!

Safe coilin' to you, George!

-- Bert H --