Re: [TCML] Terry's Filter

[Gary Lau <glau1024@xxxxxxxxx>]

Hi Bumba,

I put up a web page documenting my thoughts on how a Terry filter works.
 This is the long answer -
http://www.laushaus.com/tesla/protection.htm

The short answers are - you can use the resistor and capacitor values the
same, regardless of the voltage of your NST.  No formula is needed.  You
could use a much lower wattage resistor than the 113W units I used - you
might get away with as low as 10-20 Watts (YMMV).

There are three protection mechanisms used in a Terry filter (R-C filter,
MOV's, safety gap), all independent of each other.  The MOV's are not
compulsory, any more than air bags are compulsory in a car.  They
are separate from the seat belts, but both are good ideas.  If you do
choose to use MOV's, be advised that the number of MOV's needed is
absolutely dependent on the NST voltage, and you will need to use fewer
than if you had a 15kV NST.  If you use more than the correct number, it
won't offer any protection at all, and if you use fewer than the correct
number, you'll just smoke the MOV's.

Bear in mind that the Terry filter was originally designed for use with a
midpoint-grounded NST.  Is your 5kV NST midpoint grounded?

Regards, Gary Lau
MA, USA


On Wed, Jan 11, 2012 at 12:32 PM, Bumba Lodh <bumba007lodh@xxxxxxxxx> wrote:

> I made my tesla coil with 5KV 30ma NST.With 30nF 20KV rated MMC.I
> don't want to lose my expensive NST.So i want to built Terry's NST
> Filter for protection.Any suggestion for me?
> Whats the formula to calculate the capacitance for filter?MOV are
> compulsory?
>
> PLEASE HELP ME!!!!!!!!!!!!!!!!!!!!
> _______________________________________________
> Tesla mailing list
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