Re: Yet another newcomer, and xfmr protection
Sent: Thursday, August 28, 1997 5:50 PM
To: Tesla List
Subject: Re: Yet another newcomer, and xfmr protection
We use a small ferrite core inductor (toroid) with 10 turns of #18 AWG (pvc
insulated) connected directly to each neon bushing and then another 500
turn air core inductor in series with this. Total inductance is 5.5
milliHenry. Good range is 3-10 milliHenry for total inductance. The 500
turn inductor is made by using a piece of delrin (plastic) with a 1/4 inch
wide groove cut 1/2 inch deep in a 1 1/2 inch dia delrin rod. Five total
grooves with approx 100 turns scramble wound into each groove. Also use
three 500 pf doorknob caps in series off of each bushing to ground. A
resistor of approx 100 ohms x 25 watts in series with each bushing would
also help but we usually don't use these. Keep your primary sparkgap in
parallel with the xmfr and keep the setting tight until everything is in
tune. Don't exceed a total pri gap of 1/4 inch with a neon system and your
xmfr will last a long time assuming you have a good xmfr to begin with.
Hope this helps out.
> 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.
> I'm doing this right. Going to try to build a neon transformer system
> winter. I read somewhere that putting the spark gap across the
> 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,
> 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.
> is right?
> Dale Pfaffle
> Yerington, Nevada
> > 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
> > >most northerly tesla coiler. I'm near Huntsville, Alabama, USA. From
> > >limited experience, I've found US neon transformers to be very easily
> > >burnt out by high voltage spikes; I recommend not only chokes, which
> > >have, but bypass capcacitors (from each HV line to ground), and a
> > >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
> > terrible (2") arcing between my tank circuit and ground (like the
> > of my secondary and gap cooling fan). Malcolm Watts on this list
> > out that my chokes were being shock-excited by the spark gap, just as
> > 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