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>

Since I'm feeling so verbose today I'll take a crack at it ;-)

Your filter configuration is a little unusual, I'm not sure what the purpose
of the middle terminals is.  I would recommend connecting your NST to the
LINE terminals 1A & 3A, and your power source to LOAD terminals 1B & 3B.
Connect 3rd wire AC ground (not RF ground) to case (and/or maybe terminal
2B?).  This configuration has the caps-to-ground on the "quiet" side of the
common-mode inductors, forming a proper low pass filter.

I think a single 27 Amp filter should be adequate for your 1 or 2 15/60
NST's.  Your fuse or circuit breaker would probably trip before you got
anywhere near overcurrenting a single filter.  If you really wanted to be
conservative on the current rating, you could wire the "B" terminals of two
filters in parallel and have each pair of "A" terminals going to individual
NST's.  I don't know how you'd configure two in series - I don't think they
were designed to be cascaded.

Regards, Gary Lau
Waltham, MA USA


>Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<vanyo-at-echoes-dot-net>
>
>I posted this question a while back, but got no response.  The topic
>seems to be in vogue, so I'll try again.  Ive got four Sprague line
>filters rated 27 amp that I'd like to use for my upcoming (and first)
>coil.  The schematic (actually the scanned label on the filter) is here:
>
>http://www.geocities-dot-com/billvanyo/emifilter.jpg
>
>These are asymmetric, no?  Are they suitable for Tesla coil use?  I have
>no idea about the best way to hook these up.  I can use all four, and
>was thinking of two parallel strings of two.  Now something I read
>somewhere gives me the idea that the two in series could be in opposite
>directions, but I don't know if the it's  the line or load ends that
>should be connected together, and whether the grounds should go to the
>house or RF ground.
>
>BTW, I'll be using one or two 15/60 NST's.
>
>	Thanks,
>	Bill