On Friday 22 January 2016 12:51:17 Jim Craig wrote: > Hey all, > > I have been troubleshooting some noise that I have on my servo > encoders. I have isolated the noise source to be the 1/4hp Automation > Direct GS1 VFD that I have running my coolant pump. If the coolant > pump is not running then there is no noise on the encoders and the > machine maintains correct positioning. If I turn the coolant pump on > then the encoders get false signal that in turn changes where the > machine thinks it is. This problem showed up immediately after I > retrofitted the machine this last summer. I have just now been able to > diagnose where the issue is originating. > > In attempts to improve the situation I have done the following. > Installed EMI filters on the supply lines to both the coolant and > spindle vfds. > worked on ground system to try to isolate the noise. > rerouted the coolant pump motor power cable completely away from > any other cables and completely away from the machine. > > All of these things have failed to improve the noise issue. > > I also tried the following to try and diagnose the issue. I > disconnected the coolant pump motor cable from the coolant pump vfd. > Disconnected the spindle motor from the spindle vfd. Connected the > coolant pump to the spindle vfd. Note that the spindle vfd is a 3.0hp > Automation direct GS2 drive. > > When I did this and ran the coolant pump via the spindle vfd there was > no noise on the encoders. > > Does anyone have any ideas on how to get rid of this issue. I really > want to make some parts but I can't with the noise issue. > > I talked to a EE buddy of mine and he mentioned running both motors > (spindle and coolant pump) off the same 3.0hp GS2 drive just to get me > going. What do you think about this? Will running two different sized > motors on the same VFD cause any issue. Right now I don't run my > spindle in reverse so I would not have any trouble with the coolant > pump running backwards. > > I talked to Automation Direct and they said that the GS1 is more prone > to noise than the GS2. I am contemplating getting a 1/2hp GS2 to > replace the GS1. > > So frustrated right now. > > Let me know if you have any ideas. > > Thanks, > > Jim
Sound like a ground loop Jim. I am a firm convert to single point grounding. Can you disconnect the grounding on the encoder cable? If so, and you can measure continuity between the disconnected grounding wire and that single point ground, then you have another ground someplace. It needs to be run down and disconnected at the encoder end of the cable, so that the encoders own circuitry should use the "shipped in on the cable" ground, not some noisy frame ground. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
