Re: Line filter -- where to ground it?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>


Hi Antonio,

Interesting.   I can think of several passive filters that are not 
symmetrical.  A simple one pole RC low pass filter being driven by a 
zero impedance source needs the R in series and between the source 
and the shunt C to be effective.  If the filter is turned around 
where the shunt C is directly across the zero impedance source, there 
will be no filtering action.

With a line filter, I have seen many designs where there was only one 
common mode choke and that was between the "load" end (noise source) 
and the line to line Y caps at the line end.  This filter would not 
filter common mode noise if the filter was turned around.

Please tell me more of what you are thinking.

Gerry R.




Tesla list wrote:
> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Forest,
>
> The only added comment I have is wiring the filter in "backwards".
> Most filters are designed to keep stuff from getting back onto the 
> line cord. Some filters are symetrical and how you wire it would not 
> matter.  If your filter has a LOAD end and a LINE end, I would wire 
> it up that way and NOT wire it "backwards".
>
> Gerry R.
Passive filters, supposing resistive impedances on both sides, are 
always symmetrical. Of course this is not true if there are voltage 
limiting devices at just one side.

Antonio Carlos M. de Queiroz