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Re: tuning



Tesla List wrote:
> 
> > > > Subject: magnifiers
> > > Subject: Re: magnifiers
> > Subject: Re: magnifiers
> 
> Subscriber: bert.hickman-at-aquila-dot-com Fri Jan  3 22:09:52 1997
> Date: Fri, 03 Jan 1997 09:58:10 -0800
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: magnifiers
> 
> Tesla List wrote:
> >
> > > > Subject: magnifiers
> > > Subject: Re: magnifiers
> >
> > Subscriber: mwade-at-aros-dot-net Thu Jan  2 23:11:06 1997
> > Date: Thu, 02 Jan 1997 19:47:04 -0800
> > From: MIKE WADE <mwade-at-aros-dot-net>
> > To: tesla-at-pupman-dot-com
> > Subject: Re: magnifiers
> >
> > Tesla List wrote:
> > Bert:
> >         Thanks for the consideratoin in evaluating my system. Following is the
> > additional info. which I think you may see some red flags come up upon
> > evaluating.
> >
> > caps: 2- basically R.H. style design rolled LDPE and HDPE totalling
> > .0275uf (measured).
> > primary coil: 30 deg. conical, 10 turns 1/2" refridge tubing (tapped at
> > about 8) 7" i.d. , 20" o.d., 1/4" spacing.
> > secondary coil: 4" dia., 22" high, 24ga.
> > pwr. supply: 1- 12kv. 30 ma. neon
> > toroid: 27" o.d., made from 5" AL flex duct and spaced 7" from top of
> > coil form.
> > Gap: single static air blast -at- about 1/2" setting
> >
> >         As far as tuning, signal generator input to sec. shows resonant freq.
> > to be same as o scope observed freq. that the pri. is running at- is
> > this a valid analysis technique?
> >         I have been playing with decreasing the coupling by raising sec. up
> > away from pri. with little if any change. Had not thought toroid spacing
> > heigth mattered much in operating characteristics- thought technique was
> > to just raise it high enough so no discharges occur to pri. circuit. I
> > have no trouble getting discharge to free air as is, and adjustments to
> > pri. tap show very noticeable changes in discharge.
> >
> > Hey, I'm really with 'ya as far as  meaningless pseudo- science out
> > there! I am thankful for this great forum to exchange repeatable,
> > observable studies in this area! You're right about time passing when
> > things are running smoothly!
> >         Thanks, and I look foreward to your analysis.
> >
> > Mike
> >
> 
> Mike,
> 
> Thanks for the additional info.
> 
> General comments:
> The first problem I see is that your 12 KV 30 MA neon is heavily
> overloaded by the tank cap. This transformer is optimally sized for
> about 0.0066 uF, and could drive up to 0.01 uF - but 0.0275 uF is much
> too big. Based upon the size of your secondary, toroid, and primary it
> does look like you're in the right ballpark from a tuning standpoint.
> However, the use of 1/2" copper tubing is larger than necessary for a
> coil this size, and, combined with only 10 turns, results in relatively
> low primary inductance, forcing the need for large tank capacitance to
> bring the system into tune. Your system is basically starved for power!
> Also, the static gap spacing of 0.5" looks a little bit long for a 12 KV
> transformer.
> 
> The tank cap you've got would be ideal for a 120 MA source, but is
> necessary for system tune with your existing primary. If you can get
> them cheap, go for it... there's no substitute for power. However, the
> secondary may not be able to handle this level of input power unless you
> reduced the gap spacing a bit, and the added current may also strain the
> quenching capability of your air blast gap. If you are not already doing
> so, you may need to use compressed air in a true air-blast configuration
> to quench.
> 
> Near-term, I'd suggest removing one of the caps, and adding one more 12
> KV 30 in parallel to better match the smaller tank capactitance. Also,
> reduce the gap spacing a bit. With 0.0138 uF and two 12 KV 60's you'll
> be close to 60 Hz resonance. Don't open the gaps too widely - you WILL
> blow the weakest link (usually the neon, but sometimes the tank cap).
> You'll also need to reduce toroid capacitance to bring the system back
> into tune. Try using a pair of pie-pans, and 4" aluminum dryer duct to
> make a 15" x 4" toroid, and reduce the toroid-to-secondary spacing a bit
> to compensate for the reduced shielding and to reduce the toroid's
> isotropic capacitance a bit. Retune the system via the signal generator
> and oscilloscope - you should be able to regain tuning by moving the tap
> closer to the outermost turn.
> 
> Use a nail or screw point-up on the toroid to adjust high power tuning.
> BTW, if you don't already have one, be on the lookout for a variac.
> You'll need it to better ramp up and control the power.
> 
> Good luck, Mike - Keep us posted on how you're doing!
> 
> Safe synergizing to ya!
> 
> -- Bert --


  Bert:

	Thanks for the most helpful analysis. There are actually two postings
from you for me to address...sorry it's taken me a few days to respond,
as there was much for me to chew on! I used 1/2" because I had it. Had
no idea how to optimize cap vs. neon. Nice to hear I can use a 120 ma.
neon, and wonder if I could use a 14.4kv. 1500VA potential I have my eye
on. I am currently using a true compressed air gap. 

	Your comments regarding toroid size and spacing most facinating...had
no idea such an intricate relationship was at work. If I follow, my
current size toroid is too big because of the capacitance added to the
sec. and the tuning implications thereof. Suppose I will learn these
things as I go along.

	I am pleased to tell you that your suggestions to lower the toroid
really did the trick. Took it from 7" down to about 2" and viola! -all-
traces of winding discharge and the corona envelope between pri. and
sec. completely disappeared.I even lowered the sec. back down into the
pri. with no signs of overcoupling, etc. I didn't even change the too
wide gap spacing. I realize that the main result of running at this gap
will shorten neon life, and am keeping the run times as short as
possible- just long enough to get readings. Not much fun, but I'm
getting there!

	As regards your second post to me regarding signal generator tuning and
determination of approx. k , I had not thought to tune the pri. in this
fashion, I have been placing one of the pri. leads through a  toroid
current transformer made with several turns of loosly wound insulated
wire on a plastic spool and observing the output across a several K load
with my scope. I think I like your way better. Although this seems a
great way to see current waveform in pri. circuit. Can even see the
nodes go by when it should be quenching.

As soon as I read the procedure to determine k the lightbulb went on,
and much of years gone by engineering courses came back to me. Think I'm
on the right track now. Suppose critical coupling won't be much of an
issue 'till I get "MORE POWER!!!".

Guess I'm doing pretty well to get what I'm getting from this wimpy
30ma.'er...at least a dozen or so simultaneous 14" bright voilet
discharges, some of them usually fairly beefy, and relatively large
areas surrounding the discharges ionizing like large violet cloud.

	Thanks again for the help, and will be in touch as I impliment your
suggestions.

Mike