Hi Doug et al, Two things spring to mind : If we take the position that the LISN is an accurate representation of the line impedance (as set in the standards) the there no option other than to deal with the inrush current and "fix" it (or find something in the standard that addresses this issue directly) . However, if we decide that the LISN is at fault then it seems that (for this problem) negotiation with the standards body is required.
I take your point though regarding the resonances inherent in design of the LISN though. Chas On Fri, Dec 10, 2021 at 4:44 AM James Pawson (U3C) < [email protected]> wrote: > This message originated outside of DISH and was sent by: > [email protected] > > Hi Doug, > > > > Thinking aloud here: > > > > This strikes me as more of a flicker/inrush current kind of problem, > whereas conducted emissions would be more of a steady state problem. > > > > In the AC mains flicker test it’s a “stiff” supply and a series impedance > over which to measure the inrush current. In your case, the DC supply > inrush probably won’t be dictated by EMC standards but by system > performance, acceptable dips in supply rails, decoupling, etc. > Inductance/capacitance of the interconnecting supply lines will probably be > less than that created by the LISN. > > > > Conducted emissions are always there when the equipment is running. To my > knowledge tests aren’t commonly carried out during power transitions, maybe > for this very reason? > > > > If the power bus to the EUT isn’t “primary” of “platform” power in the > context of a military or automotive standard, or if the cables don’t > resemble an AC mains distribution network, where does the requirement to > measure conducted emissions come from? > > > > If the power is only derived from the source unit that toggles the power > to it, and if that source unit only powers this one device, then conducted > emissions might be better measured on the input to the source device > instead? > > > > Interesting issue. > > > > Anyway, hope this helps. > > James > > > > > > > > > > James Pawson > > The EMC Problem Solver > > > > *Unit 3 Compliance Ltd* > > *EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : > Consultancy* > > > > www.unit3compliance.co.uk | [email protected] > > +44(0)1274 911747 | +44(0)7811 139957 > > 2 Wellington Business Park, New Lane, Bradford, BD4 8AL > > Registered in England and Wales # 10574298 > > > > > > *From:* doug emcesd.com <[email protected]> > *Sent:* 10 December 2021 04:00 > *To:* [email protected] > *Subject:* Re: [PSES] unusual conducted emissions question > > > > Not a car. The power to our EUT is cycled by a a device. To put it on the > other side of the LISN would not mean much as we have no control of that > device. And even if we did that, the continuous interruption of the DC > current would still send the LISN into oscillation at each current edge. > > > > Doug Smith > > Sent from my iPhone > > IPhone: 408-858-4528 > > Office: 702-570-6108 > > Email: [email protected] > > Website: http://dsmith.org > ------------------------------ > > *From:* Ken Javor <[email protected]> > *Sent:* Thursday, December 9, 2021 7:55:05 PM > *To:* [email protected] <[email protected]> > *Subject:* Re: [PSES] unusual conducted emissions question > > > > The purpose of a LISN when testing for vehicular use is to simulate the > common impedance between battery and fuse block. > > There should be no power cycling “behind” the LISN, because in the vehicle > there is no switch between battery and fuse block other than the ignition > switch itself. > > Therefore the power cycling device goes between the LISN output and the > switched load. > > Ken Javor > Phone: (256) 650-5261 > > ------------------------------ > > *From: *Douglas Smith <[email protected] > <https://urldefense.proofpoint.com/v2/url?u=http-3A__doug-40emcesd.com&d=DwMFAw&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=kavBu9H9umaS2l7Zwzp81cdwEgTt9UJa3f56hflvA8A&s=OVcQCPr1r2j4G99wMQoHdTA8Uh-Ecshq2eAiFJgY7Xc&e=> > > > *Reply-To: *Douglas Smith <[email protected] > <https://urldefense.proofpoint.com/v2/url?u=http-3A__doug-40emcesd.com&d=DwMFAw&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=kavBu9H9umaS2l7Zwzp81cdwEgTt9UJa3f56hflvA8A&s=OVcQCPr1r2j4G99wMQoHdTA8Uh-Ecshq2eAiFJgY7Xc&e=> > > > *Date: *Fri, 10 Dec 2021 00:16:51 +0000 > *To: *<[email protected] > <https://urldefense.proofpoint.com/v2/url?u=http-3A__EMC-2DPSTC-40LISTSERV.IEEE.ORG&d=DwMFAw&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=kavBu9H9umaS2l7Zwzp81cdwEgTt9UJa3f56hflvA8A&s=RMadKU3rlYA8dxMrL249JcSU5tJZbNiPKINvJSO5bwo&e=> > > > *Subject: *[PSES] unusual conducted emissions question > > Hi All, > > I have come across an unusual conducted emissions issue with a device > where the impedance stabilization network for automotive testing itself > causes a problem that will not let a class of equipment ever pass because > of the network not the equipment itself. > > In this case, the power is cycled every second and the device that does > that is behind the network as that is not being tested. The interrupted > power goes through the network (12 Volts) and to the EUT. We got to the > point where we replace the EUT with a DC load, 10 Ohm resistor in parallel > with a 10 uF cap, to simulate the inrush current. That combination fails at > the low end of the frequency spectrum a lot because the network, just a > collection of L, C, and R is ringing at each power transition. > > Any thoughts? Seems like an artifact of the standard. The device cycling > power is a lab circuit and not part of the test and so should be behind the > network. > > Doug > > > - > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. 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To post a message to the list, send your e-mail to < > [email protected]> > > 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 <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher <[email protected]> > David Heald <[email protected]> > > > ------------------------------ > [image: AVG logo] <https://www.avg.com/internet-security> > > This email has been checked for viruses by AVG antivirus software. > www.avg.com <https://www.avg.com/internet-security> > > > <#m_4837240357128654504_m_-5117934351548589395_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > - > ---------------------------------------------------------------- > > 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 < > [email protected]> > > 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 <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher <[email protected]> > David Heald <[email protected]> > -- Charles Grasso Dish Technologies (c) 303-204-2974 (h) 303-317-5530 (e ) [email protected] (e2) [email protected] - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
