Re: Yet another newcomer, and xfmr protection

From: 	Dale F. Pfaffle[SMTP:pfaffle-at-tele-net-dot-net]
Sent: 	Thursday, August 28, 1997 1:23 PM
To: 	Tesla List
Subject: 	Re: Yet another newcomer, and xfmr protection

I'm new to this List (8/27/97) and not to old on the internet either. Hope
I'm doing this right.  Going to try to build a neon transformer system this
winter. I read somewhere that putting the spark gap across the transformer
was supposed to keep the large spikes and major RF out of the transformer
winding. Does this work?  If it does, why use the other configuration, cap.
across the transformer, if you can eliminate the resistors and chokes?
Also, I thought one was to avoid resonance of the transformer with the
primary capacitor.
John Freau mentions that this resonance is a good thing. Makes sense. What
is right?
Dale Pfaffle
Yerington, Nevada  

> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
> Subject: Re: Yet another newcomer, and xfmr protection
> Date: Wednesday, August 27, 1997 16:56
> From: 	Gary Lau  27-Aug-1997 1502[SMTP:lau-at-hdecad.ENET.dec-dot-com]
> Sent: 	Wednesday, August 27, 1997 2:22 PM
> To: 	tesla-at-pupman-dot-com
> Cc: 	lau-at-hdecad.ENET.dec-dot-com
> Subject: 	Re: Yet another newcomer, and xfmr protection
> >Your long message is very interesting. Perhaps you set a record for the
> >most northerly tesla coiler. I'm near Huntsville, Alabama, USA. From my
> >limited experience, I've found US neon transformers to be very easily
> >burnt out by high voltage spikes; I recommend not only chokes, which you
> >have, but bypass capcacitors (from each HV line to ground), and a safety
> >spark gap set just high enough to prevent arcing at the normal output
> >voltage of the neons. More experienced coilers tell me 5 millihenry
> >inductance per choke and 500 picofarads each side of the bypass
> >capacitor.  But I believe the safety spark gap, although the simplest
> >precaution, is the most important....  <snip>
> Agreed in full, but incomplete.  I was using a 15KV/30ma NST with 9 mH 
> chokes, 600pF caps, and safety gaps on each side.  As such, I was seeing
> terrible (2") arcing between my tank circuit and ground (like the bottom
> of my secondary and gap cooling fan).  Malcolm Watts on this list pointed
> out that my chokes were being shock-excited by the spark gap, just as my
> tank circuit was, and were ringing at their self resonant frequency.
> The solution was to add some high power resistors in series with the
> chokes (I used 3K/50W).  This fixed the arcing.  I now don't believe a
> choke/cap protection circuit should be used without series resistance.
> Gary Lau
> Waltham, MA