From: whit3rd@gmail.com   
      
   On Monday, January 29, 2018 at 10:15:10 AM UTC-8, et...@whidbey.com wrote:   
   > Reecently I helped a neighbor connect a Chinese made CNC plasma table   
   > ...manual shows a filter on  a sense wire and I don't know   
   > exactly what to do about it....    the connection   
   > diagram for this sense shows it being wrapped a few times through a   
   > ring.   
      
   Yep, that's a common-mode filter, usually a lossy ferrite bead,   
   sometimes a split bead and plastic housing that clamps over the   
   cable.   Washers might work, but (one hopes) a ferrite would   
   be slightly better because steel can magnetize and cores for   
   this purpose ought not to do that.   
      
   Since the purpose of such a filter is to deal with unwanted interference,   
   there's   
   no real calculation to selecting the core and number of turns.   
   What works, is starting with the smallest core and least turns, doing trials,   
   and when   
   the bad symptoms die down, use the next larger size or one extra turn.   
      
   If you  have an emissions test lab available (I did), watch the emissions   
   measured,   
   and omit the 'next larger size' step.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)