I read in !emc-pstc that ssel...@yorkemc.co.uk wrote (in <e18ohm0-000bwv...@anchor-post-31.mail.demon.net>) about 'dmax test' on Fri, 28 Feb 2003: >I agree that switch-on is the most likely culprit in a EMC sense, and that the >cooling of mitigation devices (thermistors etc) is important. I was merely >pointing out that the standard specifically states: "switch off the EUT before >the end of the 1 min measuring time interval" I suppose its conceivable that >voltage changes could occur, it depends what a particular EUT actually does >when you click the switch.
A voltage change obviously occurs when the load is removed from the supply. My point is that this change has no element of the nature of inrush. Some might think that there is a 'outrush'! > Maybe contact bounce comes into it? Contact bounce and making and breaking speeds differ between switches, which is why you must use the equipment's OWN switch to switch on and off. When developing the test, we tried to use a solid-state relay driven by a phase-detector that would switch at 0, 90, 180 and 270 degrees relative to a positive-going zero-crossing of the supply voltage, because that would require just four measurements to get a meaningful result. But we found that the equipment's own switch gave different results (a 20% lower average inrush current in the relevant experiments). -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
