Replacing the unshielded spindle motor cable with a shielded cable and grounding the shield in the electrical panel is probably going to yield the maximum bang for the buck.
Your DIN rail mounted ground terminals in the bottom of your panel are a good single point ground for a star configured grounding scheme, IMO. The only hassle might be getting the shield from the VFD cable down there. I think you were smart to put the VFD on the right side of the electrical panel and the PC on the left side. As I previously mentioned, with radiated noise, distance is your friend. If you're getting noise inside the PC, you might want to put a cover on the PC enclosure. My CNC panels use bare motherboards mounted to the subpanel, but some shielding is good. BTW - Electromagnetic radiated noise has an electric field and a magnetic field. Sometimes you'll seem to have more of one than another. Aluminum will block an electric field but isn't as good at attenuating a magnetic field. A steel panel attenuates magnetic fields better. Mu metal is the best electromagnetic shielding but typically isn't practical for this sort of problem. You can use a couple of small C clamps to hold sheet metal over an open chassis hole to do a real world test to determine how effective it'll be before spending time fabricating a cover only to learn that it doesn't reduce the noise. I also liked your comment about using a spectrum analyzer to quantify the noise. Noise problems can be counter intuitive and it's difficult to fix a problem if you don't know what it is, or even where it is. If good wiring practices result in intolerable noise, I might sprinkle a few magic ferrite beans around in a blind attempt to fix a specific problem, but if that doesn't work I'll quickly proceed to step 2, which involves the digital storage oscilloscope. /“When you can measure what you are speaking about, and express it in numbers, you know something about it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts advanced to the stage of science.”// // // - Lord Kelvin// / On 05/11/2015 10:44 PM, Tom Easterday wrote: > Thanks for all the info Bruce! I suspect you are right that it is radiated > noise. I should probably start with the outbound motor wire from the VFD. > It is about 5 ft. long and not shielded. There are also a couple other > cables I can shield as well that current aren’t. > -Tom > > ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
