John Kasunich wrote: > Even better, if you can get some, is a braid that can be expanded enough > to run the three motor leads through it, then stretched lengthwise so it > snugs down around the motor wires. Again, connect one end directly to > the motor frame, and the other directly to the VFD ground. > > The idea here is to have the return path for stray currents as close as > possible to the outgoing path.
There are cables produced just for this purpose with a braid and outer plastic sheath. You can also get them with 2 wires extra for temperature sensor if the motor have such. It will contain noise carried by the cables provided it is connected to a good ground at least at both ends. Additional grounding along the path improves efficiency. Ground by using clamps around the braid and against the ground rail. Pigtails act as inductors and render it less efficient at higher frequencies. And of course a spiral conductor around the leads is just a mechanical protection. It is a coil, and thus not effective at AC which is what worries us here. Any ground cable that might carry noise (current spikes) should have as large surface as possible. That means many thin strands. The grounding strap from engine to chassis of modern car is a good example. Welding cable is also fine. It should go in a straight line, never coil it up. Use mentioned straps to ground your cabinets to the machine frame and each other. Use the grounding bolts built into the cabinet for this purpose, or if there is none, make sure there is no paint or corrosion hindering a good connection when you install it yourself. Don't forget to ground the cabinet door using 1 or 2 straps. Also make sure your machine have a good connection to the grounding system of your building. If you run sensor cables or data cables to the machine cabinet, those should also be shielded and connected at both ends, and the device at the other end must be considered just another machine cabinet (grounding). This last point is less strict if using galvanic isolations, and no worry if using plastic/glass fibre. Then with the appropriate filters installed, you should be able to run your machine while your wife watches the football game. ;-) Einar ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
