Re: LCR Protection filters

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Terry,
           I tried exactly that approach once and for the first and 
only time killed a NST. By the time you have a low enough shunt 
resistance to dampen the response of the filter, there is little 
protection impedance left. Passive filters rely on terminating 
impedances to work correctly and the impedance at the terminals of a 
NST is bith high and ill-defined. I gave my filter a Butterworth 
response but the terminating impedances were mainly included in the 
filter itself. I still wouldn't use chokes.

Regards,
Malcolm

On 4 Oct 2001, at 16:30, Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> Hi All,
> 
> Just when you think it is safe to write off chokes in protection filters,
> :D  I should mention that if you place a resistor across the choke coil so
> as to critically damp the LC's natural frequency, you may have a good
> filter.  This was from Dr. Cadd's father's notes.  I did a little study of
> this and it looked like it would work perfectly well.  The resistor
> absorbed the "ring energy" much like in the RC configuration.  I think the
> LCR would be more complex than the RC configuration, but the LCR circut
> should work...  It may have better cutoff and other advantages but it
> really is not well studied... (yet...)
> 
> Cheers,
> 	
> 	Terry
> 
> 
>