Brian, You can try a low leakage 3-phase EMI filter design. This is where your magnetic stage(s) are unchanged and three existing large Y-caps are tied together to form a wye configuration between phases; the center tie point of the wye is not directly earthed. Instead, use a fourth Y-cap tied between this central node and earth. I think of this point as an artificial neutral.
In essence you can make the three large caps nearly as large as you like, just be sure they're all the same value and the voltages will nearly cancel with respect to earth, give or take a few volts based on a slight mismatch of the three. And the leakage current to earth through cap #4 should be very small. Play around with the value of that fourth cap to optimize RF common mode emissions and simultaneously keep line frequency leakage current low. BTW, VFDs are one of the worst to deal with for EMC. Good luck, Doug Douglas E Powell 970-646-3732 (m) Laporte, Colorado USA On Fri, Feb 16, 2024, 2:24 PM Brian Kunde <bkundew...@gmail.com> wrote: > I am working on an Industrial Machine with a 3-phase 5hp motor driven by a > VFD. To pass the EMC conducted emissions requirements, we had to add a RF > Line Filter that is recommended by the VFD manufacturer. This filter has > large Y-Caps. I know these currents theoretically cancel out in a balanced > system, but when performing the traditional Touch Current test according to > IEC 60990 6.2.2.2, Fault Condition No. 1 (open Protective Conductor) we > measure a current about 50mA. > > However, the standard says that "this subclause do not apply to reliably > earthed equipment. . . .". This Industrial Machine is either permanently > wired or it can use an industrial grade plug and socket, so this fault test > would not apply. > > So even though the measured current is high if we perform this fault test, > because the machine is well grounded I do not have to do anything? > > In contrast, the IEC 62368 would require a warning label, warning in the > manual, and a secondary PE terminal. > > I have read comments online such as, "in the industrial environment, they > don't give a hoot about leakage current." Is this true? > > On the other hand, an industrial machine could be the size of a building > and have dozens of VFD driven motors and line filters creating a huge > amounts of currents in an unbalance environment. So in my case, do I have > any concerns other than to insure the machine is well bonded to PE during > installation? But isn't this a normal installation consideration? > > Thanks to all. > The Other Brian > ------------------------------ > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to > EMC-PSTC@LISTSERV.IEEE.ORG > All emc-pstc postings are archived and searchable on the web at: > https://www.mail-archive.com/emc-pstc@listserv.ieee.org/ > > Website: https://ewh.ieee.org/soc/pses/ > Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to > unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> > List rules: https://ewh.ieee.org/soc/pses/listrules.html > > For help, send mail to the list administrators: > Mike Sherman at: msherma...@comcast.net > Rick Linford at: linf...@ieee.org > > For policy questions, send mail to: > Jim Bacher at: j.bac...@ieee.org > ------------------------------ > > To unsubscribe from the EMC-PSTC list, click the following link: > https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 > - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to EMC-PSTC@LISTSERV.IEEE.ORG All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/emc-pstc@listserv.ieee.org/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: msherma...@comcast.net Rick Linford at: linf...@ieee.org For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
