Re: Line Filter

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Jason,

It depends on what your AC wiring has.  Obviously, if you have three
phases, a neutral, and a ground wire (5-wire) it is easy. :-)  Like me you
probably have three wires like on the stove and dryer.  Two lines and that
"other wire", the lines simply go to L1 and L2 and you can cap off the
connections to L3 on the filter.  You then need to investigate the third
wire and determine if it is neutral or ground.  Ideally they are the same
but....

If you trace the wire back to the fuse panel and find some big heavy ground
wire that is well connected and the distance is short, you can probably
trust the third wire as both ground and neutral.  If the distance is long
or the grounding is in question, consider that wire as neutral and
independently ground the case of the filter.  It is "best" to have a nice
independent ground for the filter and always consider the third wire as
neutral but that is more easily said than done.  In my case, the dryer
outlet travels six feet to the fuse panel where the neutral is connected to
an inch thick ground cable that is bolted to the core of the planet.  So I
am pretty confident it is a good ground even though the neutral wire is
also connected directly to it.  My house was wired in 1927, so today's
standards are obviously better...

That is the general idea.  In the good old days they used the neutral wire
as ground even though it carried return current.  Today they always carry a
separate ground wire that should never carry any current unless there is a
fault so it is "really a ground".  Of course, powerful RF currents really
need to be grounded much better than any house wiring ground can provide.

Hope that helps.

Cheers,

	Terry

At 06:50 AM 7/18/00 -0700, you wrote:
>Hello everybody,
>
>I have got a 40 amp 3 phase 250/440 volt line filter from 
>Potter Wesson. I plan to use it on my control box to protect 
>my variacs etc. The only problem is I'm not exactly familiar 
>with 3 ph. It has 5 termnals on it: Gnd, N, & L1-L3. The 
>ground terminal is pretty obvious, but the N (I'm assuming 
>means nuetral or something to that effect) and L1, L2, & L3 
>I don't know how to hook up. Can I just tie N to L1, and L2 
>to L3 and use the N/L1 terminals as one hot, and L2/L3 
>termainals as the other on my 120/240 mains? Also the N, & 
>L1-L3 are in a line above the Gnd and have corresponding N, 
>L1-L3 terminals on the other side (10 terminals total) one 
>side Line the other Load as one would expect.
>
>Thanks in advance,
>Jason Johnson
>
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