Because many tests showed that these values are often extreme outliers that affect the average disproportionately. It happens with toroidal transformers; if the previous switch-off left the core magnetized and at switch-on, the current is in the same direction, the core saturates hard and the current is limited only by the primary winding resistance. This current is typically 3 or more times the average, but the occurrence of such large currents is very rare in practice.
With best wishes DESIGN IT IN! OOO Own Opinions Only www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. -----Original Message----- From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] Sent: 10 August 2017 17:13 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Inrush Current Just curious to why delete the highest and lowest values before taking the average? Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Thursday, August 10, 2017 5:00 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Inrush Current Look at Annex B of IEC/EN 61000-3-3. I did a lot of work on this for that Annex and you will often get different results each time, because of differences in how the current is interrupted at the previous switch-off. You do not select a point on the voltage waveform for the switching instant; you can't, anyway, because you must use the product's own mains switch (unless it doesn't have one). You switch at random points, because that is what happens in practice. For duration, you leave the mains voltage applied until the inrush transient is over (look at the current waveform); this is usually after three or fewer cycles, but for some products it can be rather longer. Normally, the first current peak is the highest, but occasionally the second peak is higher. With best wishes DESIGN IT IN! OOO - Own Opinions Only http://www.jmwa.demon.co.uk/ J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. From: Kim Boll Jensen [mailto:k...@bolls.dk] Sent: 10 August 2017 12:30 To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Inrush Current Hi We have several times been asked to test Inrush Current and have this function on our Harmonic tester, but it is not defined how it measure and we get very different measurements each time we switch ON the same EUT. I can't find an IEC definition on the measurement other than "peak current". I asume that it is most correctly to measure the current by switching ON at the top of the sine (90 deg), but what about duration? A peak current with a duration of 0.1 ms is not as interresting as the same current for 1 ms. And what if there are several current peaks after each other such as ringing wave form? Best regards, Kim Boll Jensen - ---------------------------------------------------------------- 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 <mailto: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 List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <mailto:sdoug...@ieee.org> Mike Cantwell <mailto:mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <mailto:j.bac...@ieee.org> David Heald <mailto:dhe...@gmail.com> ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ - ---------------------------------------------------------------- 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 <mailto: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 List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <mailto:sdoug...@ieee.org> Mike Cantwell <mailto:mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <mailto:j.bac...@ieee.org> David Heald <mailto:dhe...@gmail.com> - ---------------------------------------------------------------- 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 <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>
