Re: RC filter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Illicium Verum <sebas@xxxxxxxxxxxxxxxx>

Hello Zan?,
Neon sign transformers often fail when a high frequency signal from the primary
coil tries to go back into the NST. In the RC filter (resistor & capacitor) the
capacitor acts like short circuit when a high frequency signal tries to get
true, preventing the NST from being damaged. The signal that is being blocked
is called frequency cut off. This means only signals below this frequency are
allowed to pass true. It is advised to use a RC filter in combination
with a safety spark gap adjusted on the peak voltage of your NST
(2121 volt) In the filter that Terry designed are some MOV's (Metal
oxide varistors) added as a third security. I haven't calculated the
cut off frequency of the "Terry filter" but asume it is a frequency that will
do fine on most Tesla coils. But if you want to calculate everything
by hand you can use the following formula.

     1
___________ = Fc
2xRx"Pi"xC

This is the formula to calculate the frequency cut off, which is the frequency
from where is being blocked.

Fc = Frequency cut off in Hertz
R  = Resistance in Ohm
C  = Capacitance in Farad

In the order of pressing the buttons: 2 x "PI" x R x C = ?? (Write this 
number down)
Now divide ?? by 1 to get the cut off frequency.

I forgoth to tell that you that you have to make 2 RC combinations,
because you have to protect 2 output connectors on your NST, and these
2 RC combinations will be your RC filter.

I hope this answerd your question?
Best regards,
Sebastiaan


Monday, June 20, 2005, 3:51:53 AM, you wrote:

> Original poster: ZanJohnZakIV@xxxxxxx

> What size RF (RC) filter do I need for a 60Hz. 3.8A 120V Pri 15KV 30ma Sec
> NST and why?  How do I go about building it?  Please help me out, thanks.





--
Best regards,
Sebastiaan