For the record the reason that MIL-STD-461 forbids using shielded power wires for EMI testing is because even if a particular load gets shielded power from the pointof-distribution (circuit breaker or fuse box), that doesn¹t means the electrical power bus between the point-of-generation and distribution is shielded. In the vast majority of cases, it is not. So it is cheating to shield power between test sample and LISN and pretend that emissions can¹t leak out, or that strong fields can¹t couple directly to power lines.
Only on those platforms where power is shielded from point-of-generation to point-of-distribution and from there to the load is it possible to tailor the standard and allow shielded power for EMI testing. Another possibility is unshielded power from point-of-generation to point-of-distribution, or even elsewhere, then brick wall filtering and shielding from that point on. But that isn¹t a typical installation, either. Ken Javor Phone: (256) 650-5261 From: Patrick <conwa...@gmail.com> Date: Tue, 15 Jan 2019 15:52:00 -0700 To: Ken Javor <ken.ja...@emccompliance.com> Cc: <EMC-PSTC@listserv.ieee.org> Subject: Re: [PSES] MIL-STD-461 and power cables sanity check yes, agree completely: customers and suppliers can agree to tailor where it makes sense... and that tailoring can be contained within the contract. On Tue, Jan 15, 2019 at 3:13 PM Ken Javor <ken.ja...@emccompliance.com> wrote: > Disagree totally. Unless the Customer pre-emptively states otherwise > contractually, MIL-STD-461F/G are very clear that power is not to be shielded > during EMI testing, regardless of the platform installation wiring diagrams. > > This was always meant to be the case, but it was abused precisely as below and > that is why the blanket prohibition against shielding was inserted in ³F² and > retained in ³G.² > > Ken Javor > Phone: (256) 650-5261 > > > > > From: Patrick <conwa...@gmail.com> > Reply-To: Patrick <conwa...@gmail.com> > Date: Tue, 15 Jan 2019 14:19:32 -0700 > To: <EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: Re: [PSES] MIL-STD-461 and power cables sanity check > > ( not really addressing your question, but possibly of interest...). Note that > 4.3.8.6 explicitly states cable assemblies shall simulate actual installation > and usage. If your installation requirements include shields on all cables, > including primary power, then a discussion with the procuring authority is > needed, with possible tailoring, to make sure test configurations meet > expectations. > > > > On Tue, Jan 15, 2019 at 9:27 AM James Pawson (U3C) > <ja...@unit3compliance.co.uk> wrote: >> Hi Ken, >> That makes sense, thanks for the clarification. >> James >> >> >> >> From: Ken Javor <ken.ja...@emccompliance.com> >> Sent: 15 January 2019 15:34 >> To: EMC-PSTC@LISTSERV.IEEE.ORG >> Subject: Re: [PSES] MIL-STD-461 and power cables sanity check >> >> The issue is with primary power: that supplied by the platform to electrical >> and electronic loads. It does not apply to secondary power developed in a >> load and supplied to another load. It has nothing to do with dc vs. ac. If a >> load were supplied with 28 Vdc power from an aircraft platform and >> subsequently converted that to say 24 Vac at 400 cycles to run some other >> circuitry, the dc power would be subjected to the wording you cited, but the >> ac power would not. >> >> Ken Javor >> Phone: (256) 650-5261 >> >> >> >> From: "James Pawson (U3C)" <ja...@unit3compliance.co.uk> >> Reply-To: "James Pawson (U3C)" <ja...@unit3compliance.co.uk> >> Date: Tue, 15 Jan 2019 08:21:24 -0000 >> To: <EMC-PSTC@LISTSERV.IEEE.ORG> >> Subject: [PSES] MIL-STD-461 and power cables sanity check >> >> Hello all, >> >> MIL-STD-461 has a requirement for any conductors in a cable assembly carrying >> ³primary power² i.e. AC power from a vessel distribution bus to be separated >> out from the main cable bunch and routed separately in a test setup (clause >> 4.3.8.6). It also states that the primary power cables shall not be shielded. >> >> I understand the rationale for this, the explanatory notes at the end of the >> standard are most helpful. >> >> My interpretation is that: >> >> 1. this only applies to AC power buses (like those referenced in MIL-STD-1399 >> <http://everyspec.com/MIL-STD/MIL-STD-1300-1399/MIL-STD-1399-300B_13192/> ) >> and not to DC power supplied from another part of the EUT or from some >> Associated Equipment >> 2. power supplied in this fashion can be supplied within a shielded cable if >> that is what is specified in the final installation >> >> Having not done any MIL-STD work before I just wanted to make sure my >> interpretation was correct? >> >> Many thanks as always, >> James >> >> >> James Pawson >> Unit 3 Compliance >> >> >> - >> ---------------------------------------------------------------- >> >> 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-p...@ieee.org> >> >> All emc-pstc postings are archived and searchable on the web at: >> http://www.ieee-pses.org/emc-pstc.html >> >> Attachments are not permitted but the IEEE PSES Online Communities site at >> http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used >> formats), large files, etc. >> >> Website: http://www.ieee-pses.org/ >> Instructions: http://www.ieee-pses.org/list.html (including how to >> unsubscribe) <http://www.ieee-pses.org/list.html> >> List rules: http://www.ieee-pses.org/listrules.html >> >> For help, send mail to the list administrators: >> Scott Douglas <sdoug...@ieee.org> >> Mike Cantwell <mcantw...@ieee.org> >> >> For policy questions, send mail to: >> Jim Bacher <j.bac...@ieee.org> >> David Heald <dhe...@gmail.com> >> - >> ---------------------------------------------------------------- >> 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-p...@ieee.org> >> >> All emc-pstc postings are archived and searchable on the web at: >> http://www.ieee-pses.org/emc-pstc.html >> >> Attachments are not permitted but the IEEE PSES Online Communities site at >> http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used >> formats), large files, etc. >> >> Website: http://www.ieee-pses.org/ >> Instructions: http://www.ieee-pses.org/list.html (including how to >> unsubscribe) <http://www.ieee-pses.org/list.html> >> List rules: http://www.ieee-pses.org/listrules.html >> >> For help, send mail to the list administrators: >> Scott Douglas <sdoug...@ieee.org> >> Mike Cantwell <mcantw...@ieee.org> >> >> For policy questions, send mail to: >> Jim Bacher <j.bac...@ieee.org> >> David Heald <dhe...@gmail.com> >> - >> ---------------------------------------------------------------- >> >> 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-p...@ieee.org <mailto:lt%3bemc-p...@ieee.org> > >> >> All emc-pstc postings are archived and searchable on the web at: >> http://www.ieee-pses.org/emc-pstc.html >> >> Attachments are not permitted but the IEEE PSES Online Communities site at >> http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used >> formats), large files, etc. >> >> Website: http://www.ieee-pses.org/ >> Instructions: http://www.ieee-pses.org/list.html (including how to >> unsubscribe) <http://www.ieee-pses.org/list.html> >> List rules: http://www.ieee-pses.org/listrules.html >> >> For help, send mail to the list administrators: >> Scott Douglas <sdoug...@ieee.org <mailto:lt%3bsdoug...@ieee.org> > >> Mike Cantwell <mcantw...@ieee.org <mailto:lt%3bmcantw...@ieee.org> > >> >> For policy questions, send mail to: >> Jim Bacher <j.bac...@ieee.org <mailto:lt%3bj.bac...@ieee.org> > >> David Heald <dhe...@gmail.com <mailto:lt%3bdhe...@gmail.com> > >> > -- > // > Patrick > - > ---------------------------------------------------------------- > > 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-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > > - > ---------------------------------------------------------------- > > 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-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used > formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> -- // Patrick - ---------------------------------------------------------------- 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-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
