Re: neon vs. potential transformer

From: 	Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
Reply To: 	elekessy-at-macquarie.matra-dot-com.au
Sent: 	Wednesday, July 16, 1997 6:04 AM
To: 	Tesla List
Subject: 	Re: neon vs. potential transformer

> Peter,
> Yes, normal neon transformers can draw double or more their rated
> wattage, it all depends on the size of the tank capacitor.  Certain
> capacitance values will result in an equal but opposite reactance
> to the leakage reactance of the transformer.  The result is that a
> 60 Hz low frequency resonant condition is created.  Effectively,
> the current limiting feature of the transformer is "neutralized",
> allowing the transformer to draw more current.  The use of this
> "resonant charging" effect is one of the secrets of neon TC
> performance.
> I forget the formula for calculating the proper capacitor size offhand,
> but someone will probably post it again.   A .007uF capacitor works
> well with a 12kV, 30ma trans, and a .014uF works well with a 15kV,
> 60 ma trans.
> A potential transformer is a type of transformer used by the electric
> ulitility companies for measuring the voltage on their high voltage
> power lines.  These transformers are very well made, very robust,
> and have low losses.  Two of these transformers used together can
> approach the performance of a pole or distribution transformer.
> Unfortunately, they can be hard to obtain.
> I use a special "series-rotary" synchronous spark gap on my TCs,
> which might just help their performance a little.  I suspect however
> that a well made, multiple static gap with air or vacuum quench may
> equal or come close to the sync-gap in performance, but I can't be
> sure about that.  There's been a lot of postings on the list cautioning
> coilers not to open up their gaps too wide to prevent transformer
> destruction.  To obtain maximum spark output however, it is necessary
> to use a maximum gap setting.  I have not destroyed any neon
> transformers since I've been using safety gaps, but still, the possibility
> of destruction is there.
> I also like to use more than the usual number of turns in both the
> primary and secondary coils.  I use from 25 to 35 turns in the primary
> and about 1500 turns in the secondary.  But many coilers have
> obtained very good results using far fewer turns, so I can't say for
> sure how important this is either.  In general, it would seem that more
> turns would raise the surge impedance of the tank, and lower the
> percentage of power lost in the spark gap.
> It is important to use the correct sized toroid.  A toroid that is too
> small will produce numerous simultaneous spark streamers but they
> will all be short.  A toroid that is too large will not allow the spark to
> reach it's full length.
> Finally the coupling between the primary and secondary should be
> adjusted for best performance.  I obtain the best performance with
> my systems using a k value of about .12 or so.
> Good luck with your projects,
> John Freau


Thanks for all the usefull info. Actually I have cooked one of my neons
by opening my gap too wide, even with safety gaps but as most of my
neons came from the re-cycling place at the tip, I can't vouch for their
quality in the first place.

I am intending to replace my 3 1/2" secondary with a 6" soon, so
theoretically I should be able to run more turns on my primary as you
suggest and hopefully get a bit better performance. I also have a theory
that lower freq coils seem to produce longer spark - have you found this
to be so?


Peter E.