Correct, so for multiple duty cycles or varying loading intervals, possible solution would be to use windowed average (queue size based on 1/f and dT/dt and previous sample interval) with a 'delayed' least-squares fit thru the maxima to see if flat. [hear the ghosts of my math instructors yelling at me to use polynomial regression].
Brian From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Friday, January 06, 2017 3:32 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Thermal equilibrium - 10% rule Standards can't necessarily cover every possibility. For cyclical effects, I would say that conditions are stable if two successive temperature maxima are equal (within a reasonable tolerance). This doesn't necessarily work if more than one cycle frequency is involved, in which case you have to look for the repetition of the whole sequence, which might take a long time. For example, a 10 minute cycle and a 12 minute cycle give a sequence that repeats every 60 minutes. If you are lucky. 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. From: Doug Powell [mailto:doug...@gmail.com] Sent: Friday, January 6, 2017 11:09 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Thermal equilibrium - 10% rule Thanks! I'll take a look. I generally log with LabView or direct into an Excel spreadsheet, maybe I can get an Excel VB Script to post expected times. One of the concerns I am dealing with now is how to determine stability when there are cyclical operations going on. I am using the prescribed stability criteria and using this on the minima/maxima of the temperature variations as it moves up and down. Funny, as I sit starting at thermal data moving in this way, I think of it "porpoise-ing" up and down. All the best, Doug -Doug - ---------------------------------------------------------------- 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>
