RE: Why do TC's use line filters wired in reverse

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Gary.Lau-at-compaq-dot-com>

After smoking a 30 Amp EMI filter, I looked at the filter circuit more
carefully, and found that it DOES matter, a great deal, which way (line or
load terminals to NST) it is hooked up.  It all depends upon what you tie
the filter case terminal to.  If you tie the filter case to the 3rd wire AC
ground, then you need to hook up the filter with LINE terminals to the NST,
and LOAD terminals to the power source.  If you do like me (which I DON'T
recommend) and tie the filter case to RF ground (and to the NST case, etc),
the LOAD terminals should go the NST, and the LINE terminals should go to
the power source.  The reason I connected the case to RF ground was that I
didn't have a 3rd wire ground connection available at the filter.

If you don't connect the filter case to anything, then it probably doesn't
matter which way you hook up the input/output, but I think the filter's
effectiveness will be diminished.

The filter circuit is not symmetrical in-to-out, see the schematic.  There
are very high voltage transients between a running coil's RF ground and the
3rd wire AC ground.  If the connections are not made as recommended in the
previous paragraph, these transients will be applied directly across the
filter's internal caps that connect to the case terminal (and possibly
smoking them as I did).  And the filter will do a very poor job at keeping
the transients out of your household wiring.  I have a page on my web site
that details this.  See:
http://people.ne.mediaone-dot-net/lau/tesla/emifilter.htm

Terry, do your AC EMI filters not have the case terminal asymmetrically
connected as my schematic shows?

Gary Lau
Waltham, MA USA

>Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
>Hi All
>
>I deal with a lot of line filters at work.  All the ones I have ever seen
>are exactly the same electrically going from "in to out" as opposed to "out
>to in".  The terminals may be different on each end, but they are
>electrically the same either way...
>
>I also checked a bunch of standard line filters I use here and they are
>symetrical too.  The only TC filter I know of the is "out to in" critical
>is my NST ouput filter (see how I am :-)) at:
>
>http://hot-streamer-dot-com/TeslaCoils/Misc/NSTFilt.jpg
>
>Cheers,
>
>	Terry (the Fritz one :-))

>> I'm curious. Almost every time I see a reference to the use of line
filters
>> in
>> TCs, the user speaks of wiring them in reverse.  >>
>> If they are
>> designed for exactly what we need them to do, then why do coilers wire
them
>> in
>> reverse? I would imagine that the LC network inside these filters will
not
>> work
>> as well, and in fact may be totally useless, if used in the wrong 
>>direction.