I'm sorry to hear that the Rasmi filter didn't help your noise problems. I bought four of them, and I've installed the first one but am 1-3 days away from finally installing that electrical panel and testing the electronics.
Without the Rasmi filter, my CNC router has some noise on the VGA monitor. Sometimes it's barely noticeable, and sometimes it causes a lot of screen flicker. It's VFD frequency (spindle speed) specific. Occasionally, it will blank the screen, which makes controlling the CNC router "interesting". I tried clamp on ferrite toroids on the VGA and monitor power cables and that helped a little. The big problem is the way I ran several feet of the monitor cables adjacent to the spindle motor cable. I knew better, but hoped the motor cable shielding would be sufficient. I bought better quality double shielded VGA cable but haven't tried that yet. I should rerun the spindle motor cable far away from any data cables. The Rasmi filter is used to filter conducted noise. It attenuates the electrical noise that might be conducted on the incoming power lines. The Rasmi filter does nothing to attenuate radiated noise that's broadcast by the VFD and the spindle motor cable. This type of noise is analogous to a radio signal that's transmitted through the air, as opposed to being conducted on wires. I suspect radiated noise might be a lot of your problem. The spindle motor cable is a transmitting antenna. All of those other wires in the panel are receiving antennas. Good wiring practices can help, as you've already mentioned. I route power cables in one wireway and data cables in other wireways. It's a nonlinear world, so when a data cable needs to cross a power cable, have them cross at 90 degree angles and don't run them adjacent to each other. Use shielded cable. Shielded spindle motor cable will help prevent the VFD from transmitting radiated noise. Shielded cable for sensitive data signals will help prevent them from receiving the radiated noise signals. Shielding the noise source and the sensitive signals fights the noise at both ends. Keep as much distance as possible between high current lines (particularly the spindle motor cable between the VFD and spindle motor as it has some high frequency switching noise that radiates very well). Distance is your friend. The electromagnetic coupling is in inverse proportion to the square of the distance between the receiver and transmitter. Twice as close results in four times the noise. Four times as close gets you sixteen times as much noise. Shielded twisted pair for data cables (like Cat5 ethernet cable) is particularly noise immune because the shield blocks a lot of the radiated noise, and the noise that makes it through is greatly attenuated by twisting the cable which greatly reduces the common mode noise in those lines. Ground the cable shield at one end only. Usually, the shield is terminated at the source. In the case of the spindle motor cable, I'd ground the shield in the electrical panel next to the VFD. For most applications, I like a star grounding configuration where all of the grounds terminate at one common grounding post. Scrape off any paint and use a star washer to bite into the metal and tighten it enough to make a good gas proof electrical connection that won't corrode in a year or so and cause a high impedance path to ground. A single ground point prevents current loops, where there is a current flowing between two or more ground points. In some special circumstances, you might have better results with a power ground and a data ground, or an analog ground and a digital ground. With two completely separate ground systems, the low voltage electronics won't be subjected to a few volts of ground float noise from a noisy power device like a VFD. If the two subsystems need to have a common reference voltage, the two ground systems can be connected by a resistor (typically 1K to 100K) and/or an RF choke to allow the common voltages of both subsystems to float to the same voltage while attenuating AC noise. Pretty panel wiring is usually less noisy, particularly where radiated noise is concerned. I hope that helps. Good luck slaying the noise gremlins. On 05/11/2015 09:00 PM, Tom Easterday wrote: > Early on we made a decision to put our VFD into the same cabinet as the rest > of the electronics on a lathe retrofit - I originally had two separate > cabinets, one for power with vfd and one for electronics. This was to save > space and bring the size of the cabinet on the machine down to a more > reasonable size so it might fit through doors, etc. In retrospect, perhaps > that was a bad idea. But here we are trying to address VFD induced noise > problems. The cabinet is shown in a picture here: > https://www.flickr.com/photos/37438950@N00/17219261571/in/album-72157651167328249/ > > <https://www.flickr.com/photos/37438950@N00/17219261571/in/album-72157651167328249/> > There is actually more wiring completed now then what is shown in the > picture but you get the idea. > > After having read about folks often using Rasmi input power filters to solve > noise issues I purchased one from ebay and installed it today. It didn’t > help, and may have actually made the problem worse. I installed it very > close to the VFD input power terminals as recommended. > > When I run the spindle motor on it’s lowest RPM I hear a high pitched whine > (at the motor) and strange things begin to happen in Axis. Windows pop up, > perhaps a homing window, perhaps a touch off, perhaps Axis switches to MDI > mode, sometimes it turns the machine off, sometimes it turns the machine off > but the spindle keeps moving! Sometimes the VFD shuts off and displays "oL > 1” on the screen. > > So now I want to understand how this noise is getting into the PC. I first > thought it was because the keyboard, mouse, and video cables ran past the VFD > in the cabinet and noise was being induced on the keyboard cable. So in > trying to isolate where the issue was I disconnected those cables and ran > them far away from the VFD. No help.. I then wondered if it was coming in > the AC power to the PC, so I rerouted the PC power to a completely different > outlet outside of the cabinet. No help. I then rerouted the network and > video cables to get those away from the VFD, no help again. Even with the > door open (as you see in the picture) I have noise. The only thing > connecting the PC to the rest of the system is the parallel cable which is > about 12” long that connects to the Mesa 7i85s card (and again, that is at > the other end of my cabinet from the VFD). Today I borrowed a friend’s > 0-1Ghz spectrum analyzer to see if I can find the source/frequency of the > noise and/or where it might be getting to the PC. I will start playing with > that tomorrow. > > I am wondering if anyone has any ideas of where i can look, or what I can do? > -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 > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
