Customers sometimes want both the highest peak current and an rms over a defined number of line cycles. If the request is exclusively standards based, John's suggestion works well. You'll need to perform five to ten tests randomly closing on the supply cycle and pick the highest values.
If an rms value is also needed, you can capture the inrush on a scope and gate the measurement over the relevant number of line cycles. Regards, Peter Tarver From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Thursday, August 10, 2017 05:32 Well, no-one has challenged Annex B since it was first included in the standard. Note that the standard applies up to 16 A/phase, so no big motors, etc. From: Nyffenegger, Dave [mailto:dave.nyffeneg...@bhemail.com] Sent: 10 August 2017 13:15 I think it also depends on what your EUT is. Machinery will typically be full of all sorts of loads, motors, transformers, power supplies, computers, inductive, capacitive, etc. The inrush would still be the peak current when the mains is switched on or also when the machine is started as they are typically two separate events. These could last several seconds depending on the machinery and the incoming power sine wave would probably have little effect on it. -Dave From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Thursday, August 10, 2017 8:00 AM 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. From: Kim Boll Jensen [mailto:k...@bolls.dk] Sent: 10 August 2017 12:30 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 <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>
