Re: [Emc-users] VFD causing limits to trip. Huh?
The problem is there are no low impedance ground available. The mains power cable ground is not low impedance at high frequency and the common mode voltage of inverters will couple a high frequency current into the ground cable. The trick usually used is to isolate logical ground and increase common mode resistance to reduce the ground current which also will lower the high frequency ground voltage. From the outside you machine have two or more power cables and one ground cable. There will be a capacitance between each output phase from the inverters and ground. This capacitance connected to ground is switched between the lowest and highest input voltage which of course will make a high frequency current flow into the high frequency non zero impedance ground. If you connect to a star ground inside your machine they will all bounce around with the same voltage. Nicklas Karlsson On Fri, 20 Mar 2015 17:54:23 +0100 Peter Blodow p.blo...@dreki.de wrote: Przemek, the shield picks up stray energy from the suroundings. The inside of it is a faraday cage and free of electric fields, which is what we aim at. Now, as the shield has picked up the noise energy, (re)converting electromagnetic field energy to real voltage and current, it must get rid of it somewhere. This is most quickly done by a low resistance, i.e. low impedance, shorting the noise current to ground on the sending side without reaching the signal consumer. Sorry for answering late, I was on a short trip for the last days. Peter Am 18.03.2015 17:11, schrieb Przemek Klosowski: On Mon, Mar 16, 2015 at 11:34 AM, Peter Blodow p.blo...@dreki.de wrote: Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. This is opposite to what Steve said, which was to ground near the signals are consumed, which makes more sense to me because shield potentials, if any, have smaller chance of leaking through to the signal wires. From the impedance point of view, I would also worry more about interference near high-impedance nodes rather than low-impedance nodes, just because smal currents result in larger voltages there. Can you summarize the rationale for your recommendation in the language of electromagnetics? --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Przemek, the shield picks up stray energy from the suroundings. The inside of it is a faraday cage and free of electric fields, which is what we aim at. Now, as the shield has picked up the noise energy, (re)converting electromagnetic field energy to real voltage and current, it must get rid of it somewhere. This is most quickly done by a low resistance, i.e. low impedance, shorting the noise current to ground on the sending side without reaching the signal consumer. Sorry for answering late, I was on a short trip for the last days. Peter Am 18.03.2015 17:11, schrieb Przemek Klosowski: On Mon, Mar 16, 2015 at 11:34 AM, Peter Blodow p.blo...@dreki.de wrote: Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. This is opposite to what Steve said, which was to ground near the signals are consumed, which makes more sense to me because shield potentials, if any, have smaller chance of leaking through to the signal wires. From the impedance point of view, I would also worry more about interference near high-impedance nodes rather than low-impedance nodes, just because smal currents result in larger voltages there. Can you summarize the rationale for your recommendation in the language of electromagnetics? --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
If one is trying to minimize radiated interference from a signal source, then grounding the shield at the source end makes sense. My suggestion of grounding the shield at the consumer of the signals was based on reducing the likelihood of a hostile external noise source confusing the consumer. Steve Stallings -Original Message- From: Przemek Klosowski [mailto:przemek.klosow...@gmail.com] Sent: Wednesday, March 18, 2015 11:12 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] VFD causing limits to trip. Huh? On Mon, Mar 16, 2015 at 11:34 AM, Peter Blodow p.blo...@dreki.de wrote: Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. This is opposite to what Steve said, which was to ground near the signals are consumed, which makes more sense to me because shield potentials, if any, have smaller chance of leaking through to the signal wires. From the impedance point of view, I would also worry more about interference near high-impedance nodes rather than low-impedance nodes, just because smal currents result in larger voltages there. Can you summarize the rationale for your recommendation in the language of electromagnetics? -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
I also agree about this. Nicklas Karlsson On Wed, 18 Mar 2015 12:43:16 -0500 Steve Stallings steve...@newsguy.com wrote: If one is trying to minimize radiated interference from a signal source, then grounding the shield at the source end makes sense. My suggestion of grounding the shield at the consumer of the signals was based on reducing the likelihood of a hostile external noise source confusing the consumer. Steve Stallings -Original Message- From: Przemek Klosowski [mailto:przemek.klosow...@gmail.com] Sent: Wednesday, March 18, 2015 11:12 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] VFD causing limits to trip. Huh? On Mon, Mar 16, 2015 at 11:34 AM, Peter Blodow p.blo...@dreki.de wrote: Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. This is opposite to what Steve said, which was to ground near the signals are consumed, which makes more sense to me because shield potentials, if any, have smaller chance of leaking through to the signal wires. From the impedance point of view, I would also worry more about interference near high-impedance nodes rather than low-impedance nodes, just because smal currents result in larger voltages there. Can you summarize the rationale for your recommendation in the language of electromagnetics? -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On Mon, Mar 16, 2015 at 11:34 AM, Peter Blodow p.blo...@dreki.de wrote: Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. This is opposite to what Steve said, which was to ground near the signals are consumed, which makes more sense to me because shield potentials, if any, have smaller chance of leaking through to the signal wires. From the impedance point of view, I would also worry more about interference near high-impedance nodes rather than low-impedance nodes, just because smal currents result in larger voltages there. Can you summarize the rationale for your recommendation in the language of electromagnetics? -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On Mon, Mar 16, 2015 at 4:40 PM, Karlsson Wang nicklas.karls...@karlssonwang.se wrote: I think you are right and will just try to dig a little bit deeper. A shield is primarily intended to prevent electrostatic coupling from the outside world. So by grounding in the consuming end the shield will get the ground potential of the consumer and the signal cables will be shielded from different external electric fields. This should motivate why as you say the shield should be connected in this end only. If there are current there is also a potential difference. I consider the VFD to be a noise source since it have common mode voltage which will emit an electrical field. There is also a capacitance between the VFD cables and shield. Since Shield impedance on high frequency is far from zero the shield around the VFD cables will not be at GND potential. The most common method is to increase common mode inductance by a filter but I have also seen active filters which reduce the common mode voltage and multiple step voltage inverters. Nicklas Karlsson A shield has two primary jobs - keep interference from the outside getting in, and keeping the signal inside the shield from getting out. Mark -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On Tue, Mar 17, 2015 at 5:49 AM, Nicklas Karlsson nicklas.karls...@karlssonwang.se wrote: Yes a shield has two primary jobs but ground impedance is far from zero at high frequency. The shield will not stay at fixed potential at high frequency for a noise source. If there are three-phase input and a ground Cable summed current thru all four may be zero but there may be a current flow from the three-phase Cable to to ground cable. At high frequency impedance in ground cable is far from zero and there will noise on the ground cable. Nicklas Karlsson True, but as Bertho pointed out, there are a few different ways to skin a cat when it comes to shielding stray noise. Filters can be added to the cable to suppress or allow certain frequency bands, and where and how you ground the shield can also have a lot to do with what you are actually shielding from or for. Mark -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Yes a shield has two primary jobs but ground impedance is far from zero at high frequency. The shield will not stay at fixed potential at high frequency for a noise source. If there are three-phase input and a ground Cable summed current thru all four may be zero but there may be a current flow from the three-phase Cable to to ground cable. At high frequency impedance in ground cable is far from zero and there will noise on the ground cable. Nicklas Karlsson On Mon, Mar 16, 2015 at 4:40 PM, Karlsson Wang nicklas.karls...@karlssonwang.se wrote: I think you are right and will just try to dig a little bit deeper. A shield is primarily intended to prevent electrostatic coupling from the outside world. So by grounding in the consuming end the shield will get the ground potential of the consumer and the signal cables will be shielded from different external electric fields. This should motivate why as you say the shield should be connected in this end only. If there are current there is also a potential difference. I consider the VFD to be a noise source since it have common mode voltage which will emit an electrical field. There is also a capacitance between the VFD cables and shield. Since Shield impedance on high frequency is far from zero the shield around the VFD cables will not be at GND potential. The most common method is to increase common mode inductance by a filter but I have also seen active filters which reduce the common mode voltage and multiple step voltage inverters. Nicklas Karlsson A shield has two primary jobs - keep interference from the outside getting in, and keeping the signal inside the shield from getting out. Mark -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/17/2015 12:33 AM, Karlsson Wang wrote: The frequency converters I have seen for electric motors generate a square wave voltage. To generate a sinus the duty cycle is varied to get sinus voltage in average and usually the current is close to sinus. Most modern converters are class D amplifiers. One main difference is in the headroom they provide in the switch-frequency. The cheaper ones have about one order of magnitude headroom whereas the really good ones have up to two orders of magnitude headroom, frequency wise (switch frequency vs. output frequency). There is a trade-off between output accuracy and cost of switching and filtering. It all comes down to money ;-) Second, as you note, the current may be sinusoidal, but that does not mean that the voltage is sinusoidal. A motor is an inductive load, where the voltage and current are not in phase. This results in a problem for control loops where you have to choose between current based or voltage based regulation. Both have merits, but ultimately, the result of the output is in the quality of the filters in the VFD and the impedance matching between VFD, cabling and motor, which have to span a considerable frequency range. Then it come to quality I guess the large difference is in filters and coupling to control signal ground. There exist true sinus output but I think all of them are sold as true sinus for a higher price. Yes. The filters are very important. But you have to look at the system as a whole to build a good one. Components must be matched properly for best results. Non-sinusoidal drivers may be adequate for many systems, but when the power goes up, the EMI pollution generally increases too. It is a question of keeping EMI under control. Eliminating it completely is utopia. -- Greetings Bertho (disclaimers are disclaimed) -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/16/2015 09:40 PM, Karlsson Wang wrote: A shield is primarily intended to prevent electrostatic coupling from the outside world. So by grounding in the consuming end the shield will get the ground potential of the consumer and the signal cables will be shielded from different external electric fields. This should motivate why as you say the shield should be connected in this end only. If there are current there is also a potential difference. There are generally three cases to consider: 1) a shield as a Faraday cage; this means that only one side of the shield may be connected to go into the earth/ground star-point where you maintain an absolute reference of zero (0V). The shield is used to dump all (most) cable-internal EM radiation into a low-impedance star-point via the shield. 2) a shield as in a coaxial conductor; here the signal is contained in the cable and the shield is part of the conducting circuit. This works on basis of very tightly controlled cable properties and is generally limited to a specific frequency range per cable specs. 3) all other cases; the shield is connected at both sides and is intentionally or unintentionally part of the conducting circuit. This case will generally give you worse results in terms of EMI emissions and protection. The shield will radiate and may act as an antenna to worsen the situation. I consider the VFD to be a noise source since it have common mode voltage which will emit an electrical field. There is also a capacitance between the VFD cables and shield. Since Shield impedance on high frequency is far from zero the shield around the VFD cables will not be at GND potential. The most common method is to increase common mode inductance by a filter but I have also seen active filters which reduce the common mode voltage and multiple step voltage inverters. With respect to VFD systems; the amount of junk they produce depends on the quality of the converter. The best version generates a relatively pure sinusoidal output and the EMI it generates is very minimal. Such VFD can normally be connected without problem with unshielded cabling. The lesser quality emulates a sinusoidal output, but has substantial higher harmonics. These VFDs are not too shabby, but they can cause interference. The best solution is to filter the output before putting it on (long) cables. No shielding is required when the harmonics are under control, but it generally does not hurt to use a Faraday cage type shield. The cheap VFDs are poor substitutes and generate nearing square-wave output. The amount of EMI from higher harmonics is high and is often difficult to filter at the source. These VFDs should be used with both output filters and shielded cabling. The remaining problem that may arise is EMI from the motor. The remaining harmonics may radiate from the motor just as easily. That cannot be solved with shielding of the cables. You must ensure proper earthing of the motor as well and it should be enclosed in a proper metal casing. It should also be noted that VFD frequency changes cause harmonics in the output. If you turn on/off the hard way, then you can introduce some transients that are very hard to control. The best way is to control the up-/down-going frequency such that no abrupt changes can occur and therefore no transients are allowed to be created due to too fast changes. -- Greetings Bertho (disclaimers are disclaimed) -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
I would recommend that shielded signal cables have the shield grounded only at the end where the signals are consumed. If a ground is needed by the device at the end of the cable, you should use a conductor inside rather than the shield itself. If there are signals going both ways, provide the shield ground connection at the end where the most sensitive signals are consumed. The purpose of grounding only one end of the shield is to prevent current from flowing in the shield itself and distorting the signals due to electromagnetic coupling. A shield is primarily intended to prevent electrostatic coupling from the outside world. If the cable does not contain sensitive signals, such as the power cable from a VFD to the spindle, then it is acceptable to ground both ends of the shield. Steve Stallings www.PMDX.com -Original Message- From: Matt Tucci [mailto:matt2c1...@gmail.com] Sent: Monday, March 16, 2015 7:54 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] VFD causing limits to trip. Huh? Are the shielded wires only grounded at one end and at the controller end? On Sun, Mar 15, 2015 at 1:22 PM, Karlsson Wang nicklas.karls...@karlssonwang.se wrote: I think grounding is the most important. There are normally a common mode voltage at the inverter output to motor so the inverter power ground will bounce around each time inverter is switched. If this bouncing is coupled to the logic ground there may be a lot of problems. Nicklas Karlsson On Sun, 15 Mar 2015 14:39:24 + (GMT) russ...@lls.lls.com (Russell Brown) wrote: I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. I then tried a ferrite core (mains clipon stylee) on the input of the field power supply. No difference. A ferrite core (ring with both wires looped through it a couple of times) on the output of the 12V field power made no difference either. A ferrite core (ring as above) on the limit switch wires fitted at the Mesa end made no difference either. So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. Of course I don't know if this is a 100% fix or just enough to get through my failing case (other jobs without all the above have run fine). I guess time will tell. Hope that's useful for someone. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https
Re: [Emc-users] VFD causing limits to trip. Huh?
Are the shielded wires only grounded at one end and at the controller end? On Sun, Mar 15, 2015 at 1:22 PM, Karlsson Wang nicklas.karls...@karlssonwang.se wrote: I think grounding is the most important. There are normally a common mode voltage at the inverter output to motor so the inverter power ground will bounce around each time inverter is switched. If this bouncing is coupled to the logic ground there may be a lot of problems. Nicklas Karlsson On Sun, 15 Mar 2015 14:39:24 + (GMT) russ...@lls.lls.com (Russell Brown) wrote: I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. I then tried a ferrite core (mains clipon stylee) on the input of the field power supply. No difference. A ferrite core (ring with both wires looped through it a couple of times) on the output of the 12V field power made no difference either. A ferrite core (ring as above) on the limit switch wires fitted at the Mesa end made no difference either. So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. Of course I don't know if this is a 100% fix or just enough to get through my failing case (other jobs without all the above have run fine). I guess time will tell. Hope that's useful for someone. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Steve, this is a good description of noise reduction by shielding. To make it more exact, the shield should be grounded at the end where the lower impedance is, mostly the signal source. And not using the shield as a conductor is useful because any current flow in the shield would cause magnetic noise to be induced in the conductors along inside the cable. Even in power cables, grounding both ends of the shield may cause ground loops,resulting in mains frequency currents (formerly: hum) that are hard to locate. Generally, magnetic noise is harder to fight than electrostatic. Peter Am 16.03.2015 15:41, schrieb Steve Stallings: I would recommend that shielded signal cables have the shield grounded only at the end where the signals are consumed. If a ground is needed by the device at the end of the cable, you should use a conductor inside rather than the shield itself. If there are signals going both ways, provide the shield ground connection at the end where the most sensitive signals are consumed. The purpose of grounding only one end of the shield is to prevent current from flowing in the shield itself and distorting the signals due to electromagnetic coupling. A shield is primarily intended to prevent electrostatic coupling from the outside world. If the cable does not contain sensitive signals, such as the power cable from a VFD to the spindle, then it is acceptable to ground both ends of the shield. Steve Stallings www.PMDX.com -Original Message- From: Matt Tucci [mailto:matt2c1...@gmail.com] Sent: Monday, March 16, 2015 7:54 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] VFD causing limits to trip. Huh? Are the shielded wires only grounded at one end and at the controller end? On Sun, Mar 15, 2015 at 1:22 PM, Karlsson Wang nicklas.karls...@karlssonwang.se wrote: I think grounding is the most important. There are normally --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
The frequency converters I have seen for electric motors generate a square wave voltage. To generate a sinus the duty cycle is varied to get sinus voltage in average and usually the current is close to sinus. Then it come to quality I guess the large difference is in filters and coupling to control signal ground. There exist true sinus output but I think all of them are sold as true sinus for a higher price. Nicklas Karlsson On Mon, 16 Mar 2015 22:19:42 +0100 Bertho Stultiens ber...@vagrearg.org wrote: On 03/16/2015 09:40 PM, Karlsson Wang wrote: A shield is primarily intended to prevent electrostatic coupling from the outside world. So by grounding in the consuming end the shield will get the ground potential of the consumer and the signal cables will be shielded from different external electric fields. This should motivate why as you say the shield should be connected in this end only. If there are current there is also a potential difference. There are generally three cases to consider: 1) a shield as a Faraday cage; this means that only one side of the shield may be connected to go into the earth/ground star-point where you maintain an absolute reference of zero (0V). The shield is used to dump all (most) cable-internal EM radiation into a low-impedance star-point via the shield. 2) a shield as in a coaxial conductor; here the signal is contained in the cable and the shield is part of the conducting circuit. This works on basis of very tightly controlled cable properties and is generally limited to a specific frequency range per cable specs. 3) all other cases; the shield is connected at both sides and is intentionally or unintentionally part of the conducting circuit. This case will generally give you worse results in terms of EMI emissions and protection. The shield will radiate and may act as an antenna to worsen the situation. I consider the VFD to be a noise source since it have common mode voltage which will emit an electrical field. There is also a capacitance between the VFD cables and shield. Since Shield impedance on high frequency is far from zero the shield around the VFD cables will not be at GND potential. The most common method is to increase common mode inductance by a filter but I have also seen active filters which reduce the common mode voltage and multiple step voltage inverters. With respect to VFD systems; the amount of junk they produce depends on the quality of the converter. The best version generates a relatively pure sinusoidal output and the EMI it generates is very minimal. Such VFD can normally be connected without problem with unshielded cabling. The lesser quality emulates a sinusoidal output, but has substantial higher harmonics. These VFDs are not too shabby, but they can cause interference. The best solution is to filter the output before putting it on (long) cables. No shielding is required when the harmonics are under control, but it generally does not hurt to use a Faraday cage type shield. The cheap VFDs are poor substitutes and generate nearing square-wave output. The amount of EMI from higher harmonics is high and is often difficult to filter at the source. These VFDs should be used with both output filters and shielded cabling. The remaining problem that may arise is EMI from the motor. The remaining harmonics may radiate from the motor just as easily. That cannot be solved with shielding of the cables. You must ensure proper earthing of the motor as well and it should be enclosed in a proper metal casing. It should also be noted that VFD frequency changes cause harmonics in the output. If you turn on/off the hard way, then you can introduce some transients that are very hard to control. The best way is to control the up-/down-going frequency such that no abrupt changes can occur and therefore no transients are allowed to be created due to too fast changes. -- Greetings Bertho (disclaimers are disclaimed) -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Karlsson Wang nicklas.karls...@karlssonwang.se -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought
Re: [Emc-users] VFD causing limits to trip. Huh?
I think you are right and will just try to dig a little bit deeper. A shield is primarily intended to prevent electrostatic coupling from the outside world. So by grounding in the consuming end the shield will get the ground potential of the consumer and the signal cables will be shielded from different external electric fields. This should motivate why as you say the shield should be connected in this end only. If there are current there is also a potential difference. I consider the VFD to be a noise source since it have common mode voltage which will emit an electrical field. There is also a capacitance between the VFD cables and shield. Since Shield impedance on high frequency is far from zero the shield around the VFD cables will not be at GND potential. The most common method is to increase common mode inductance by a filter but I have also seen active filters which reduce the common mode voltage and multiple step voltage inverters. Nicklas Karlsson On Mon, 16 Mar 2015 09:41:15 -0500 Steve Stallings steve...@newsguy.com wrote: I would recommend that shielded signal cables have the shield grounded only at the end where the signals are consumed. If a ground is needed by the device at the end of the cable, you should use a conductor inside rather than the shield itself. If there are signals going both ways, provide the shield ground connection at the end where the most sensitive signals are consumed. The purpose of grounding only one end of the shield is to prevent current from flowing in the shield itself and distorting the signals due to electromagnetic coupling. A shield is primarily intended to prevent electrostatic coupling from the outside world. If the cable does not contain sensitive signals, such as the power cable from a VFD to the spindle, then it is acceptable to ground both ends of the shield. Steve Stallings www.PMDX.com -Original Message- From: Matt Tucci [mailto:matt2c1...@gmail.com] Sent: Monday, March 16, 2015 7:54 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] VFD causing limits to trip. Huh? Are the shielded wires only grounded at one end and at the controller end? On Sun, Mar 15, 2015 at 1:22 PM, Karlsson Wang nicklas.karls...@karlssonwang.se wrote: I think grounding is the most important. There are normally a common mode voltage at the inverter output to motor so the inverter power ground will bounce around each time inverter is switched. If this bouncing is coupled to the logic ground there may be a lot of problems. Nicklas Karlsson On Sun, 15 Mar 2015 14:39:24 + (GMT) russ...@lls.lls.com (Russell Brown) wrote: I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. I then tried a ferrite core (mains clipon stylee) on the input of the field power supply. No difference. A ferrite core (ring with both wires looped through it a couple of times) on the output of the 12V field power made no difference either. A ferrite core (ring as above) on the limit switch wires fitted at the Mesa end made no difference either. So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. Of course I don't know if this is a 100% fix or just enough to get through my failing case (other jobs without all the above have run fine). I guess time will tell. Hope that's useful for someone. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Pardon my ignorance... But is there a significant difference between use of shielded cable between VFD and motor vrs lines in hard or flex metal conduit which makes a complete ground at each end? Thanks Greg -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/16/2015 07:33 PM, Greg Bentzinger wrote: Pardon my ignorance... But is there a significant difference between use of shielded cable between VFD and motor vrs lines in hard or flex metal conduit which makes a complete ground at each end? Both cable-shield and a conducting cable-pipe will work the same for most practical purpuses. The trick for effective shields is that it should not carry the ground (current) from one side to the other. If the shield is grounded on both sides, then you most probably leak the signal at the shield (the signal is no longer contained). The *real* difference is that a (properly) shielded cable has tightly controlled impedance and coaxial properties, which is an important attribute and a requirement for most application. Using a pipe will have an impedance at some level and is not guaranteed to be the same over the entire length. The result is that you may introduce signal reflection when using a pipe(*). Usually, the shield is connected at one (!) star-point connection to earth where all earth and shield connections come together. It may then be connected from there to ground using a parallel RC 100..1000k//1..100n@1..2kV (may need to experiment with values for best suppresion). The resistor is to level any potential (static) buildup and the capacitor shorts the AC components. It is a lot cheaper to use a pipe and run some wires in there. But, as said before, you need to measure the exact impact of doing so. You may end up worse if you do it wrongly. (*) With high power signals, such as motor driving lines, reflections can overload the drivers or the feeding PSU. High-power lines should always be as short as possible and tightly impedance controlled. -- Greetings Bertho (disclaimers are disclaimed) -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On Sun, 15 Mar 2015, Kirk Wallace wrote: Date: Sun, 15 Mar 2015 07:54:46 -0700 From: Kirk Wallace kwall...@wallacecompany.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: emc-users@lists.sourceforge.net Subject: Re: [Emc-users] VFD causing limits to trip. Huh? On 03/15/2015 07:39 AM, Russell Brown wrote: I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. ... snip So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. ... snip Thank you for posting your results. I'll have to put shielding a little higher on my list. Don't forget about differential signaling, higher signal voltage and formal cable termination. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ As a general rule ferrite beads help with current noise (ground bumping for example) and are not useful on high impedance inputs while shielding helps with capacitively coupled noise (say from 350V square waves from VFD into limit switch wires) -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. I then tried a ferrite core (mains clipon stylee) on the input of the field power supply. No difference. A ferrite core (ring with both wires looped through it a couple of times) on the output of the 12V field power made no difference either. A ferrite core (ring as above) on the limit switch wires fitted at the Mesa end made no difference either. So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. Of course I don't know if this is a 100% fix or just enough to get through my failing case (other jobs without all the above have run fine). I guess time will tell. Hope that's useful for someone. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/15/2015 07:39 AM, Russell Brown wrote: I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. ... snip So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. ... snip Thank you for posting your results. I'll have to put shielding a little higher on my list. Don't forget about differential signaling, higher signal voltage and formal cable termination. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
I think grounding is the most important. There are normally a common mode voltage at the inverter output to motor so the inverter power ground will bounce around each time inverter is switched. If this bouncing is coupled to the logic ground there may be a lot of problems. Nicklas Karlsson On Sun, 15 Mar 2015 14:39:24 + (GMT) russ...@lls.lls.com (Russell Brown) wrote: I promised to report back so... I fitted the filter (Schaffner FN2030 Series 16A 250 V ac 400Hz) on the VFD mains input and that did make a difference. My failing case job ran 70% of the way through where without it the job failed 10% in. Not the complete solution though. I then tried a ferrite core (mains clipon stylee) on the input of the field power supply. No difference. A ferrite core (ring with both wires looped through it a couple of times) on the output of the 12V field power made no difference either. A ferrite core (ring as above) on the limit switch wires fitted at the Mesa end made no difference either. So... finally I replaced the limit switch wires with shielded cable (grounded only at the Mesa end). That seemed to do the final trick and the job ran all the way through. Of course I don't know if this is a 100% fix or just enough to get through my failing case (other jobs without all the above have run fine). I guess time will tell. Hope that's useful for someone. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Here http://www.beama.org.uk/en/publications/technical-guides.cfm/motor-shaft-voltages is a another pain in the regions not to far behind called bearing currents. Regards Nicklas Karlsson On Fri, 06 Mar 2015 12:34:07 -0500 Dave Cole linuxcncro...@gmail.com wrote: VFDs and AC servo drives oftentimes create noise on the incoming AC power lines to the drives.That noise can cause interference issues with system electronics. I recommend you purchase an incoming line filter to keep the noise from backing up into your AC power line. This is a filter I used on a recent installation. Put this as close to the drive/s power input connection as practical. http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_%28VFD%29_Spare_Parts_-a-_Accessories/GS_EMI_-z-_RF_Filters/EMI_-z-_RF_Filters_%28All_GS_Drives%29/20DRT1W3S There are cheaper filters available but I know that this one works. Dave On 3/6/2015 6:56 AM, Russell Brown wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Grounding is really important. Noise on logical ground usually cause communication errors and could of course trigger a limit swith, have you tried lower input impedance? A common mode filter on the output may be a good idea. I have the theoretical knowledge but limited experience. Nicklas Karlsson On Sat, 7 Mar 2015 08:44:11 + (GMT) russ...@lls.lls.com (Russell Brown) wrote: Many thanks for all the input chaps. The consensus seems to be a) Add a mains input filter. b) Shield the limit switch wires. c) Stick ferrites in. d) Mask the problem with a debounce :-) As I have a pretty solid failing case, I figure it's worth while seeing if A-C can fix it before masking the problem with a debounce. So I've ordered a filter; Schaffner FN2030 Series 16A 250 V ac 400Hz on the basis that Arceurotrade suggest them for their spindles and RS stock them :) I'll also replace the limit switch wires with twisted pair shielded and sprinkle some ferrites on the 7i76 inputs. I'll report back on the results. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
The inverter output voltage have very fast flanks to get low switching losses and the circuit is closed by the capacitance in motor to protective earth. There are usually also a capacitance between internal transistors and cooling fin connected to protective earth. The capacitances charge/discharge with the switching frequency and usually cause severe problem with digital communication unless not mitigated. I have also read there may be current thru the bearings and EDM is known method for material removal. A common mode filter rise the impedance in the loop from the power cables to the protective earth. I have also seen articles with active filters but not tried them myself yet. Nicklas Karlsson On Fri, 6 Mar 2015 14:43:00 -0500 (EST) Todd Zuercher zuerc...@embarqmail.com wrote: What sort of screen? and where is it in relation to the VFD? We have a router with 2 VFDs mounted on the outside of a wooden cabinet, and they wreak havoc on the CRT display inside the cabinet when they accelerate/decelerate (about 6 inches away). It is fine while its running, just when stopping and starting. I was thinking I should make some sort of metal shield to mount between them, but its been that way for more than 15 years without any thing more than this aesthetic problem so it hasn't been real high on my to do list. - Original Message - From: Bruce Layne linux...@thinkingdevices.com To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Sent: Friday, March 6, 2015 1:58:09 PM Subject: Re: [Emc-users] VFD causing limits to trip. Huh? My 2'X4' CNC router has a 2.2 KW water cooled spindle and VFD - the typical Chinese kit off eBay. http://www.ebay.com/itm/221354796303 I'm getting noise on the video signal that usually causes annoying screen jitter but sometimes blanks out the screen entirely, which can be a bit disconcerting when running a CNC machine. That sounds like RFI, but I used good shielded cable between the VFD and spindle motor. The shield is grounded at the VFD, and I think I upgraded to a better quality shielded video cable, so I then assumed the noise was leaking out as conducted (as opposed to radiated) interference on the VFD's power leads, although I haven't verified that with the digital storage oscilloscope. I installed some toroids as RF chokes on the incoming VFD power leads and it seemed to help a tiny bit. I almost never use that machine, so this problem wasn't high on my To Do list, but I'm building a 2'X2' CNC router for me (the larger machine was mostly for my brother), and I'd like to avoid replicating the problem on the second CNC router build. I just ordered a 14A Rasmi power line input filter on eBay for the VFD. It cost US$16 delivered. http://www.ebay.com/itm/290958532530 Hat tip to Andy for the recommendation. On 03/06/2015 12:43 PM, Andy Pugh wrote: Almost certainly EMI. An input filter for the VFD can help. Check eBay for Rasmi they are not expensive. -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/07/2015 12:44 AM, Russell Brown wrote: Many thanks for all the input chaps. The consensus seems to be a) Add a mains input filter. b) Shield the limit switch wires. c) Stick ferrites in. d) Mask the problem with a debounce :-) Another method to consider. Common inputs have high impedance so the full induced voltage from noise gets applied to the input. I have often found that the signal (the good stuff we want) can drive the input to close to 5 Volts, but the input will trip at around 2.5 Volts depending on the input type. So the noise can be weaker than the signal and still be a problem. Placing a resistor from the input to the input's ground can load the noise enough to keep it below 2.5 Volts, but still have the signal above the tripping level. Using signal drivers to utilize 12 or 24 Volt signals I believe is common for commercial machines, and they wouldn't add the cost if it were not needed. Using twisted pair is effective. The twist cancels the induced noise which also can reduce the noise below the trip level, but leave the signal alone. In my experience, shielding and differential drivers haven't been all that effective, but may be worth a try. Beyond a simple load resistor on the input, there are various methods to terminate a cable, such as terminating resistors, matched to the cable impedance, at both ends, to RC filters that can load the noise harder and leave more of the desired signal. I would leave software filtering as a last resort. Adding AC mains filters to VFD's, in my experience, has had the single biggest effect. Also, my HNC lathe had AC filters on the motor leads. When I added a VFD, they turned to smoke and puddles of plastic. The filters were trying to do their job which is to filter high frequency, but the VFD output signal is pure high frequency. I replaced the filters with ferrite beads, but this didn't seem to help much. My HNC lathe has most of the cabling running in common flexible or rigid metal conduit which may help. My mill has no cable shielding, just plain CAT5 twisted pair, input resistors, AC main filters on the VFD, and so far so good. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Many thanks for all the input chaps. The consensus seems to be a) Add a mains input filter. b) Shield the limit switch wires. c) Stick ferrites in. d) Mask the problem with a debounce :-) As I have a pretty solid failing case, I figure it's worth while seeing if A-C can fix it before masking the problem with a debounce. So I've ordered a filter; Schaffner FN2030 Series 16A 250 V ac 400Hz on the basis that Arceurotrade suggest them for their spindles and RS stock them :) I'll also replace the limit switch wires with twisted pair shielded and sprinkle some ferrites on the 7i76 inputs. I'll report back on the results. -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 3/6/2015 6:54 AM, Todd Zuercher wrote: You might be able to get away with just adding a debounce to the limit inputs. That worked for me on a machine that was giving me false trips on the X limit. I suspected mine was a dodgy cable at the time, but it might have been cross talk since it hasn't given any problems since adding the debounce. VFDs are supposed to be directly connected to the 3 phase motors, but I wonder if it's possible to add capacitors or something to smooth out the output. So far no issues running the early 1940's GE 3HP in my Monarch 12CK with a VFD. I never vary the speed from 60Hz. If it fries it *then* I'll figure out how to remove the massive thing from the base. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 3/6/2015 1:52 PM, Bruce Layne wrote: The LCD is on an articulated arm, a little above eye level, mounted to the side of the large nonmetallic enclosure. The VFD is mounted in the steel electrical enclosure about five feet lower. The cables all exit through cable clamps in holes on the bottom of the electrical enclosure. I really need to take the digital storage oscilloscope over there to quantify the noise problem. I mostly designed it with EMI in mind to prevent problems, then did a couple of quick and dirty obvious fixes (better cable routing, ferrite magic beans) that seemed likely to help but didn't. It's time to get serious, figure out the real issue and then fix it. My ears perked up when I saw this thread. I was hoping someone would fix my problem for me. :-) Magnetic interference shouldn't directly bother the LCD panel like it can a cathode ray tube. Inducing currents into the display cable via radio or magnetic interference is where you'll get the problems. The internal electronics of LCD monitors are usually quite well shielded, though more likely to contain interference rather than block it out. Could try a tinfoil hat approach. ;-) Wrap the display cable with aluminum tape then ground the ends to the not sticky side. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/06/2015 07:19 PM, Gregg Eshelman wrote: On 3/6/2015 6:54 AM, Todd Zuercher wrote: You might be able to get away with just adding a debounce to the limit inputs. That worked for me on a machine that was giving me false trips on the X limit. I suspected mine was a dodgy cable at the time, but it might have been cross talk since it hasn't given any problems since adding the debounce. VFDs are supposed to be directly connected to the 3 phase motors, but I wonder if it's possible to add capacitors or something to smooth out the output. No, you don't want capacitors directly on the output of the VFD. The sharp, 400V edges will cause high currents, and either pop the capacitors or the output transistors. What you want is a line filter module at the power input, and if that isn't good enough, then a set of 3 inductors on the output to the motor. I found a line filter on the line input cleared up some intermittent problems on my mill. I used a commercial line filter module. Jon -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Zuercher, If Gene is right, then there is a really big loop area. Ether the leads to the motor / drive are taking different paths or the is a big ground loop some place. You could try moving the leads around to confirm what Gene is suggesting. If this is the case, check for ground loops. If there aren't any, then you should consider rearranging you wiring. N. Christopher Perry On Mar 6, 2015, at 3:14 PM, Charles Steinkuehler char...@steinkuehler.net wrote: On 3/6/2015 1:43 PM, Todd Zuercher wrote: What sort of screen? and where is it in relation to the VFD? We have a router with 2 VFDs mounted on the outside of a wooden cabinet, and they wreak havoc on the CRT display inside the cabinet when they accelerate/decelerate (about 6 inches away). It is fine while its running, just when stopping and starting. I was thinking I should make some sort of metal shield to mount between them, but its been that way for more than 15 years without any thing more than this aesthetic problem so it hasn't been real high on my to do list. I know this one: You need a Mu-Metal shield. The VFD is throwing enough current around a big enough loop it's generating magnetic fields (*NOT* EMI!) and distorting the video display. It happens on speed changes because you're drawing lots of current. It should also happen if you load the motor with a deep cut and push it close to it's rated power level. Really nice broadcast studio monitors are magnetically shielded to avoid this, but just about any other CRT monitor won't be. http://en.wikipedia.org/wiki/Mu-metal And yes, a magnetic field _is_ a form of EMI (Electro Magnetic Interference), but it's at a _really_ low frequency and thus is generally not affected by the typical EMI shielding practices that are mostly concerned with very high frequency effects. You might have good luck simply turning the VFD to a different orientation (try rotating it on it's side or back and see if the problem gets any better or worse). -- Charles Steinkuehler char...@steinkuehler.net -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
Hi Russel, I got exactly the same troubles describes with the VFDs creating a lot of perturbation. Aspiration was also making perturbation for me. Thankfully at my work place we have experts on EMI and Stephen advices are what you need to follow. In my case, to solve it I had to shield the cable between the VFD and the spindle and physically separate them (away from the cable chain in my case). Limits and touch probes are now with shielded cables and ferrites. Also Shields are touching the metallic part of the connectors so as to be linked to the electronic rack. Between electronic rack, VFD generator and the machine I have metallic braids (flat and large). Linking the axis together with this braids might have helped also (and not relaying on the balls from the guiding rails). I also have a metallic plate which shield the control computer from the VFD. Good luck solving this, sometimes it work for 20 minutes without tripping a limit, but there is hope even with Chinese parts, now, for me the setup is reliable. Cheers, -- Yves Watier 2015-03-06 13:36 GMT+01:00 Stephen Dubovsky smdubov...@gmail.com: EMI. VFDs generate lots of it. You're likely getting lots of noise coupled into your limit switch cabling. Shield the vfd wires if possible. Running in a shielded single cable is probably best. Separate the motor and switch cables as much as possible too. On March 6, 2015 6:56:08 AM EST, russ...@lls.lls.com wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly
Re: [Emc-users] VFD causing limits to trip. Huh?
Wiring to the switch is damaged somewhere? On Fri, Mar 6, 2015 at 6:56 AM, Russell Brown russ...@lls.lls.com wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
EMI. VFDs generate lots of it. You're likely getting lots of noise coupled into your limit switch cabling. Shield the vfd wires if possible. Running in a shielded single cable is probably best. Separate the motor and switch cables as much as possible too. On March 6, 2015 6:56:08 AM EST, russ...@lls.lls.com wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
You could also put a reactor between the motor and drive. Might be a good idea to put a line filter on the power leads to the drive too. I'm not a fan of shielding, but it's certainly an option as well. N. Christopher Perry On Mar 6, 2015, at 7:36 AM, Stephen Dubovsky smdubov...@gmail.com wrote: EMI. VFDs generate lots of it. You're likely getting lots of noise coupled into your limit switch cabling. Shield the vfd wires if possible. Running in a shielded single cable is probably best. Separate the motor and switch cables as much as possible too. On March 6, 2015 6:56:08 AM EST, russ...@lls.lls.com wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
You might be able to get away with just adding a debounce to the limit inputs. That worked for me on a machine that was giving me false trips on the X limit. I suspected mine was a dodgy cable at the time, but it might have been cross talk since it hasn't given any problems since adding the debounce. - Original Message - From: N. Christopher Perry vwpe...@comcast.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Sent: Friday, March 6, 2015 8:10:55 AM Subject: Re: [Emc-users] VFD causing limits to trip. Huh? You could also put a reactor between the motor and drive. Might be a good idea to put a line filter on the power leads to the drive too. I'm not a fan of shielding, but it's certainly an option as well. N. Christopher Perry On Mar 6, 2015, at 7:36 AM, Stephen Dubovsky smdubov...@gmail.com wrote: EMI. VFDs generate lots of it. You're likely getting lots of noise coupled into your limit switch cabling. Shield the vfd wires if possible. Running in a shielded single cable is probably best. Separate the motor and switch cables as much as possible too. On March 6, 2015 6:56:08 AM EST, russ...@lls.lls.com wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? -- Regards, Russell | Russell Brown | MAIL: russ...@lls.com PHONE: 01780 471800 | | Lady Lodge Systems | WWW Work: http://www.lls.com | | Peterborough, England | WWW Play: http://www.ruffle.me.uk | -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc
Re: [Emc-users] VFD causing limits to trip. Huh?
VFDs and AC servo drives oftentimes create noise on the incoming AC power lines to the drives.That noise can cause interference issues with system electronics. I recommend you purchase an incoming line filter to keep the noise from backing up into your AC power line. This is a filter I used on a recent installation. Put this as close to the drive/s power input connection as practical. http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_%28VFD%29_Spare_Parts_-a-_Accessories/GS_EMI_-z-_RF_Filters/EMI_-z-_RF_Filters_%28All_GS_Drives%29/20DRT1W3S There are cheaper filters available but I know that this one works. Dave On 3/6/2015 6:56 AM, Russell Brown wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 6 Mar 2015, at 12:56, Russell Brown russ...@lls.lls.com wrote: Any ideas what might cause this? Almost certainly EMI. An input filter for the VFD can help. Check eBay for Rasmi they are not expensive. If your mill is not downstream of an RCD then I have one spare you can have. Otherwise make sure you get one with 3mA leakage current. (This point is why I have a spare) Note that these go on the input to the VFD to keep noise out of the mains wiring. But the really simple solution is likely to be the HAL debounce component. 20mS delay in a limit switch isn't critical. -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
My 2'X4' CNC router has a 2.2 KW water cooled spindle and VFD - the typical Chinese kit off eBay. http://www.ebay.com/itm/221354796303 I'm getting noise on the video signal that usually causes annoying screen jitter but sometimes blanks out the screen entirely, which can be a bit disconcerting when running a CNC machine. That sounds like RFI, but I used good shielded cable between the VFD and spindle motor. The shield is grounded at the VFD, and I think I upgraded to a better quality shielded video cable, so I then assumed the noise was leaking out as conducted (as opposed to radiated) interference on the VFD's power leads, although I haven't verified that with the digital storage oscilloscope. I installed some toroids as RF chokes on the incoming VFD power leads and it seemed to help a tiny bit. I almost never use that machine, so this problem wasn't high on my To Do list, but I'm building a 2'X2' CNC router for me (the larger machine was mostly for my brother), and I'd like to avoid replicating the problem on the second CNC router build. I just ordered a 14A Rasmi power line input filter on eBay for the VFD. It cost US$16 delivered. http://www.ebay.com/itm/290958532530 Hat tip to Andy for the recommendation. On 03/06/2015 12:43 PM, Andy Pugh wrote: Almost certainly EMI. An input filter for the VFD can help. Check eBay for Rasmi they are not expensive. -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
What sort of screen? and where is it in relation to the VFD? We have a router with 2 VFDs mounted on the outside of a wooden cabinet, and they wreak havoc on the CRT display inside the cabinet when they accelerate/decelerate (about 6 inches away). It is fine while its running, just when stopping and starting. I was thinking I should make some sort of metal shield to mount between them, but its been that way for more than 15 years without any thing more than this aesthetic problem so it hasn't been real high on my to do list. - Original Message - From: Bruce Layne linux...@thinkingdevices.com To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Sent: Friday, March 6, 2015 1:58:09 PM Subject: Re: [Emc-users] VFD causing limits to trip. Huh? My 2'X4' CNC router has a 2.2 KW water cooled spindle and VFD - the typical Chinese kit off eBay. http://www.ebay.com/itm/221354796303 I'm getting noise on the video signal that usually causes annoying screen jitter but sometimes blanks out the screen entirely, which can be a bit disconcerting when running a CNC machine. That sounds like RFI, but I used good shielded cable between the VFD and spindle motor. The shield is grounded at the VFD, and I think I upgraded to a better quality shielded video cable, so I then assumed the noise was leaking out as conducted (as opposed to radiated) interference on the VFD's power leads, although I haven't verified that with the digital storage oscilloscope. I installed some toroids as RF chokes on the incoming VFD power leads and it seemed to help a tiny bit. I almost never use that machine, so this problem wasn't high on my To Do list, but I'm building a 2'X2' CNC router for me (the larger machine was mostly for my brother), and I'd like to avoid replicating the problem on the second CNC router build. I just ordered a 14A Rasmi power line input filter on eBay for the VFD. It cost US$16 delivered. http://www.ebay.com/itm/290958532530 Hat tip to Andy for the recommendation. On 03/06/2015 12:43 PM, Andy Pugh wrote: Almost certainly EMI. An input filter for the VFD can help. Check eBay for Rasmi they are not expensive. -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
That's the big brother of the one I picked. N. Christopher Perry On Mar 6, 2015, at 12:34 PM, Dave Cole linuxcncro...@gmail.com wrote: VFDs and AC servo drives oftentimes create noise on the incoming AC power lines to the drives.That noise can cause interference issues with system electronics. I recommend you purchase an incoming line filter to keep the noise from backing up into your AC power line. This is a filter I used on a recent installation. Put this as close to the drive/s power input connection as practical. http://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_%28VFD%29_Spare_Parts_-a-_Accessories/GS_EMI_-z-_RF_Filters/EMI_-z-_RF_Filters_%28All_GS_Drives%29/20DRT1W3S There are cheaper filters available but I know that this one works. Dave On 3/6/2015 6:56 AM, Russell Brown wrote: I've just fitted one of them there 'Chinese' 2.2kW watercooled motors with a Huanyang VFD as a second spindle on my mill. Last night doing some pocketing, when the cutter got into the 'meat' of the cut (6mm carbide 2 flute, 3mm DOC), Linuxcnc (v2.6.7) tripped with Axis 2 limit switch. This was unexpected as I was nowhere near the Z-axis limit switches so I checked the connections and started the job again and it did exactly the same thing again in the same place! Just for fun, I reduced the DOC, tried again and the same thing happened in the same place (about 20 seconds into the job). H The VFD is 1 foot away from the limit switch wiring, and the connection from the VFD to the motor is shielded and grounded at the VFD end. I'm controlling the VFD with hy_vfd over RS485. The limit switches (normal microswitches bolted to the column) are wired to a Mesa 7i76 with 12V field power and have not played up before. I did an 'air-cut' and that ran well past the place it was consistently failing. I commented out: #net both-home-z = axis.2.home-sw-in #net both-home-z = axis.2.neg-lim-sw-in #net both-home-z = axis.2.pos-lim-sw-in in my Mill.hal file and the job ran to the end. Axis 0 and 1 limits were left unchanged. I ran out of time to experiment much further but I'm struggling to see how the VFD could trip a simple limit switch when it's getting a bit loaded up (the spindle was only pulling ~1amp according to hy_vfd and it's rated for 8). I don't think it was simple vibration as I'd been fly cutting with my normal spindle shortly before and that didn't trip anything. Any ideas what might cause this? --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 3/6/2015 1:43 PM, Todd Zuercher wrote: What sort of screen? and where is it in relation to the VFD? We have a router with 2 VFDs mounted on the outside of a wooden cabinet, and they wreak havoc on the CRT display inside the cabinet when they accelerate/decelerate (about 6 inches away). It is fine while its running, just when stopping and starting. I was thinking I should make some sort of metal shield to mount between them, but its been that way for more than 15 years without any thing more than this aesthetic problem so it hasn't been real high on my to do list. I know this one: You need a Mu-Metal shield. The VFD is throwing enough current around a big enough loop it's generating magnetic fields (*NOT* EMI!) and distorting the video display. It happens on speed changes because you're drawing lots of current. It should also happen if you load the motor with a deep cut and push it close to it's rated power level. Really nice broadcast studio monitors are magnetically shielded to avoid this, but just about any other CRT monitor won't be. http://en.wikipedia.org/wiki/Mu-metal And yes, a magnetic field _is_ a form of EMI (Electro Magnetic Interference), but it's at a _really_ low frequency and thus is generally not affected by the typical EMI shielding practices that are mostly concerned with very high frequency effects. You might have good luck simply turning the VFD to a different orientation (try rotating it on it's side or back and see if the problem gets any better or worse). -- Charles Steinkuehler char...@steinkuehler.net signature.asc Description: OpenPGP digital signature -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] VFD causing limits to trip. Huh?
On 03/06/2015 02:43 PM, Todd Zuercher wrote: What sort of screen? 20 LCD. Dell, I think. Where is it in relation to the VFD? The LCD is on an articulated arm, a little above eye level, mounted to the side of the large nonmetallic enclosure. The VFD is mounted in the steel electrical enclosure about five feet lower. The cables all exit through cable clamps in holes on the bottom of the electrical enclosure. I really need to take the digital storage oscilloscope over there to quantify the noise problem. I mostly designed it with EMI in mind to prevent problems, then did a couple of quick and dirty obvious fixes (better cable routing, ferrite magic beans) that seemed likely to help but didn't. It's time to get serious, figure out the real issue and then fix it. My ears perked up when I saw this thread. I was hoping someone would fix my problem for me. :-) -- Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
