Re: [Fwd: Spark gap not firing]

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

Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ludev-at-videotron.ca>

Hi Terry, list,

I'm in the process of designing a power supply and I try to find a formula to
create a RC low pass filter (Terry NST filter protection ) I look at your
paper,
on the web, I remember I read about it in the past but were ? I know if you
change the value of R and C you change at what frequency the filter start
to cut
and how fast the db cut rise with the frequency. I could apply your value but I
like to understand what I do . Can you help me to find the formula or if my
memory is good the graph to calculated it ?

Luc Benard



> snip
>
> The voltages levels by themselves are within the NST's rated maximum.
> However, what worries me is the frequency.  If and NST gets hit with 15kV
> at 60 Hz it is happy.  But think of what happens when the output terminals
> are hit with 15kV at 400kHz!  The secondary coils of the NST are not going
> to look like nice inductors anymore but rather complex L's and C's.  I
> suspect that instead of the high voltage being evenly distributed across
> the output windings, as they are at low frequency, much of the voltage is
> spread across just a few windings at high frequency.  At 400kHz, the high
> frequency voltage is just not going to get very far in the output windings
> and that high voltage my hit only a few layers and BLAMMO!  Since trying to
> figure out how the high frequency voltage distributes in the output winding
> of an NST is rather messy.  I figure it is best to simply stop it from ever
> going there...
>
> Reports like yours of NSTs taking this high frequency voltage are
> encouraging.  However, I suspect that is an exceptional case.  Since the
> strong emphasis on using protection filters, and putting the gap across the
> NST began, the number of NST failures has dropped dramatically...
>
> Cheers,
>
>         Terry
>

snip