Re: NST protection query

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

At 09:02 AM 2/8/2004, you wrote:
>My question regards the effect of frequency
>  on the protection of the NST.
>
>My NST is a 15kv30ma,
>  and although it has always proven quite sturdy,
>  generating long arcs for various experiments,
>  I have never used it for a Tesla coil.
>
>Reading the various protection schemes,
>  I see the 'Terry Filter' seems to be the
>  current vogue, but I am not sure I can get
>  the right components here <Jakarta> to build one,
>  being (perhaps) cheaper just to buy a new coil.

At least use safety gaps.

>
>That said, I am under the impression that the lower
>  the resonant frequency employed, the more
>  important the protection design should be,
>  given that if we design for higher frequency mode
>  that protection against hf backing into the NST
>  gets easier to achieve with small chokes.

The inductance of the NST secondary coils is like 2000H.  Adding chokes is 
useless.

>
>If I do run the primary at high frequency (10 mhz++)
>  then would simple chokes suffice?

Almost all coils run at 80kHz to 700kHz.  I would not worry with special 
frequencies just for protection.  10MHz would be a very extreme frequency 
for a Tesla coil and would have problems.

>
>Another thought regarding the 'self-resonant' failure
>  of chokes is that perhaps it might be best to
>  vary the 4 chokes around the safety gap
>  in order that they are all differing values
>  to avoid self-resonance? <devil in the details...>

Just go with safety gaps and LTR size primary caps.  No choke is going to 
help.  If you can get the resistors, that would help too but the LTR cap 
size and safety gaps are what really counts.

Cheers,

         Terry


>
>cheers