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Re: SIZE of RF chokes?

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi JT,

There are three lines of defense with the Terry filter.

1. Safety gap  properly set  (probably the best line of defense)

2. RC filter (the caps might go in your small space next to the NST or on top of the NST properly insulated of course). They should be grounded (with short run of wire) to NST chassis for best effect. The resisters probably dont need to be 100W for your NST size but this wattage allows growth for larger power sources (I use two 500 ohm 50 watt resisters in series for each leg on a 2KW supply and they dont get too hot). They can probably be mounted somewhere in the connection between the NST and your safety gap. Not as important as to where although closer to NST is probably better. This filter helps with the high frequency stuff that can cause carbon tracking in the tar and damage to the NST HV windings (can surface track on the winding I believe).

3. MOVs. This is a last line of defense as they will fail in short circuit mode (give their all to protect the NST). If your safety gap is properly set and you dont take a strike on the primary, you probably dont need these.

Use a safety gap if nothing else. If you can figure out the placement, you can add the RC filter and this with the safety gap will give you most of the protection. Wattage of the resisters comes from three sources I believe.

a) AC charging - about a watt in your case with 30ma NST
b) Discharge of the Terry filter caps for each bang  (0.5*C*V*V) * BPS
c) RF energy across the resisters (dont have a number on this)

Use ceramic wire wound reisters so they can take the heat. 1000 ohm 25 watt resisters on each leg ought to be enough. Here are two links that show my filter that might give you some ideas:

http://hot-streamer.com/temp/GerryReynolds/15KV_120ma_SRSG/tc11_4NSTs_with_terry_filter.jpg
http://hot-streamer.com/temp/GerryReynolds/15KV_120ma_SRSG/tc12_terry_filter.jpg


Gerry R.


Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>
I NEED HELP WITH A SAFETY CIRCUIT, DESIGNED TO BE VERY SPACE EFFECTIVE.

(I HAVE EXACTLY A 2.5" X 3" X 3.5" SPACE FOR A SAFETY CIRCUIT RIGHT NOW. OH, AND GET THIS- I ADDED A GROUNDED CENTER TO MY SAFETY GAP, AND IT STOPPED FIRING ALL TOGETHER........>>>>(WTF?????)

RESPOND ASAP

let me send an email to you, with pictures of my coil. I have tons of pictures
Whats your email.....

please 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: SIZE of RF chokes?
Date: Fri, 18 Nov 2005 20:28:17 -0700

Original poster: FutureT@xxxxxxx

In a message dated 11/18/05 1:54:50 PM Eastern Standard Time, tesla@xxxxxxxxxx writes:


>*****I would love a terry filter, but unfortunately i am a
>perfectionist, and have made my coil look very good. As a
>consequence of this, MANY components are very close together.



You may be pleased to hear that my TT-42 coil which gives 42"
sparks from a 12/30 NST, does not use any filter.  I just use
safety gaps.

   http://hometown.aol.com/futuret/page3.html

John