Re: Terry Filters - Basic Education

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: otmaskin5@xxxxxxx 

This was helpful - thanks Dr - Dennis Hopkington MA


-----Original Message-----
From: tesla@xxxxxxxxxx
To: tesla@xxxxxxxxxx
Sent: Thu, 21 Sep 2006 7:30 PM
Subject: Re: Terry Filters - Basic Education

Original poster: "resonance" 
<<mailto:resonance%40wildblue.net>resonance@xxxxxxxxxxxx>


The main function of a "Terry filter" is to block any RF currents 
from getting back into the high voltage winding of the NST. Terry 
filters do this in several ways:

First, the resistance effectively spoils the "Q" factor of the 
circuit which kills the large transient spikes.

The small capacitors allow any remaining RF currents to go directly 
to ground where they are neutralized.

The third defense is a string series of varisters. Varisters are 
variable resistors that can either block a voltage, or, then suddenly 
change into good conduction (low resistance) once a certain peak 
voltage is reached. In this way the over-voltage is shorted to ground 
as the resistance drops to a low value.

The final defense is a safety spark gap that allows any remaining 
overpotentials to jump directly to ground before entering the high 
voltage windings of the transformer.

Keeping the RF spikes out of the transformer secondary windings is 
the name of the game here.

Dr. Resonance


>Original poster: <mailto:otmaskin5%40aol.com>otmaskin5@xxxxxxx
>After putting together a Terry filter & wiring it into my TC, 
I >started wondering what this thing is supposed to do. I know, 
this >might have been a better question to ask before I built it, 
but >sometimes that's how I do things. Actually I pretty much know 
WHAT >it's supposed to do, but I haven't been able to find good 
basic >level info on HOW it does what it does - i.e., what each 
component >does. I mean basic layman level sort of like Terry filters 
for >dummies. I understand the safety gap part pretty well. But not 
the >other components. For example I know how a capacitor works, but 
I'm >not clear on how it protects the NST.
>
>Any way, I'd appreciate any info on this that any of you would 
like >to share. Thx, Dennis Hopkinton MA
>
>



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