Each line (phase and neutral) sees 50 Ohms in parallel with 50 uH, but the power port sees a differential impedance of 100 uH in parallel with 100 Ohms, and a common mode impedance of 25 uH in parallel with 25 Ohms. Ken Javor
Phone: (256) 650-5261 ________________________________ From: <ralph.mcdiar...@ca.schneider-electric.com> List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Thu, 8 Apr 2010 10:28:00 -0700 To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] 50 ohm LISN (AMN) Thank you all. I feel better now; knowledge is often comforting. Would it be correct to say that the EUT power port 'sees' an impedance of approx 50 ohms in parallel with the reactance of the inductance used in the LISN? _______________________________________ ____________________________________________ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer From: Bill Owsley <wdows...@yahoo.com> To: EMC-PSTC@LISTSERV.IEEE.ORG List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: 04/08/2010 09:41 AM Subject: Re: [PSES] 50 ohm LISN (AMN) ________________________________ We might also note that the drop in impedance as the frequency lowers is somewhat a necessity. Otherwise, operating an AC powered device through a LISN might be less than useful/functional. - Bill In the event of a national emergency, click on the following links to provide directions to your duly elected mis-representative. http://www.usa.gov/Contact/Elected.shtml <http://www.usa.gov/Contact/Elected.shtml> <http://www.usa.gov/Contact/Elected.shtml> or... https://writerep.house.gov/writerep/welcome.shtml <https://writerep.house.gov/writerep/welcome.shtml> http://www.senate.gov/general/contact_information/senators_cfm.cfm <http://www.senate.gov/general/contact_information/senators_cfm.cfm> <http://www.senate.gov/general/contact_information/senators_cfm.cfm> ________________________________ From: "Price, Edward" <ed.pr...@cubic.com> To: emc-p...@ieee.org Sent: Thu, April 8, 2010 10:04:47 AM Subject: RE: 50 ohm LISN (AMN) From: emc-p...@ieee.org [mailto:emc-p...@ieee.org <mailto:emc-p...@ieee.org> <mailto:emc-p...@ieee.org> ] On Behalf Of ralph.mcdiar...@ca.schneider-electric.com Sent: Wednesday, April 07, 2010 6:51 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: 50 ohm LISN (AMN) Two academic questions for the group: 1. When we say '50uH/50 ohm LISN' are we referring to a device which provides a source impedance of 50 ohms over its frequency range or one that must be terminated with 50 ohms? _______________________________________ _____________________________________________ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer - When we say “50 uH / 50 Ohm LISN”, we are making a couple of mental shortcuts: 1. The impedance that the LISN presents to the EUT is about 50 Ohms, plus or minus the tolerance of the design, over maybe most of the LISN’s operational frequency range. However, as an example, the LISN required by MIL-STD-461F, Figures 6 & 7, uses a 50 uH inductor, yet presents 50 Ohms to the EUT only >from about 700 kHz through 10 MHz. This LISN is used starting at 10 kHz, where the impedance presented to the EUT is only about 5 Ohms. And the impedance curve tolerance is +/- 20%. 2. The “50 uH” part of the labeling is really irrelevant. It doesn’t matter what you pack into the LISN box, as long at the EUT port impedance conforms to the governing standard. Note that I’m not trying to make a case for exotic innards, just pointing out what’s really important. So, you can see that a “50 uH / 50 Ohm LISN” doesn’t necessarily have to be built with a 50 uH inductor, and isn’t a constant 50 Ohms impedance! 3. The LISN should have its signal output port terminated in 50 Ohms at all times. This is done by attaching a 50 Ohm resistive termination to the port when the port is not being actively observed (you may be looking at another power line, or you may be doing something other than the CE102 test). When you are actually measuring this LISN’s power line, the LISN signal output should have a 20 dB attenuator (although I sometimes use a lesser value to get more sensitivity with my acquisition system). The attenuator not only works to ensure impedance accuracy, but it also protects the acquisition system RF input from transient voltages caused by sudden current changes in the LISN power current (the EUT may have large current surges at turn-on or turn-off, during operation, or during a fault or failure condition). It’s bad enough to toast the EUT, but even worse if that takes out your analyzer’s input circuitry. 4. Remember that your LISN must be verified to meet the curve of impedance presented to the EUT. Further, you must obtain a measured “port loss factor” for each LISN you use. (For the Mil-Std LISN, this factor is several dB near the low end of the frequency range.) Your acquisition system software needs this factor, which is added to the attenuator and cable loss factors, to report accurate data. Ed Price ed.pr...@cubic.com WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty - 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:emc-p...@ieee.org> <mailto:emc-p...@ieee.org> > All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc <http://www.ieeecommunities.org/emc-pstc> <http://www.ieeecommunities.org/emc-pstc> Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ <http://www.ieee-pses.org/> <http://www.ieee-pses.org/> Instructions: http://listserv.ieee.org/request/user-guide.html <http://listserv.ieee.org/request/user-guide.html> <http://listserv.ieee.org/request/user-guide.html> List rules: http://www.ieee-pses.org/listrules.html <http://www.ieee-pses.org/listrules.html> <http://www.ieee-pses.org/listrules.html> For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com <mailto:emcp...@socal.rr.com> <mailto:emcp...@socal.rr.com> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> <mailto:dhe...@gmail.com> > ________________________________________________________________________ This email has been scanned for SPAM content and Viruses by the MessageL abs Email Security System. ________________________________________________________________________ - 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:emc-p...@ieee.org> <mailto:emc-p...@ieee.org> > All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc <http://www.ieeecommunities.org/emc-pstc> <http://www.ieeecommunities.org/emc-pstc> Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ <http://www.ieee-pses.org/> <http://www.ieee-pses.org/> Instructions: http://listserv.ieee.org/request/user-guide.html <http://listserv.ieee.org/request/user-guide.html> <http://listserv.ieee.org/request/user-guide.html> List rules: http://www.ieee-pses.org/listrules.html <http://www.ieee-pses.org/listrules.html> <http://www.ieee-pses.org/listrules.html> For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com <mailto:emcp...@socal.rr.com> <mailto:emcp...@socal.rr.com> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> <mailto: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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>
