Hi John, What I learned the last few days....
The difference with clearance is that creepage needs time to create a path.... Electrochemical reactions behave like charging a battery, it is the rms value that determines the charge, not the peak value. And about being prudent, in my case a creepage path of 14 mm could be reduced to 7.5 mm , a considerable cost saver. (clearance is 6.5) Regards, Ing. Gert Gremmen, BSc [email protected] www.cetest.nl Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment. -----Oorspronkelijk bericht----- Van: John Woodgate [mailto:[email protected]] Verzonden: Tuesday, May 13, 2014 8:49 AM Aan: [email protected] Onderwerp: Re: [PSES] Creepage and RMS In message <[email protected]>, dated Tue, 13 May 2014, "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> writes: >- Creepage breakdown is an essential long time process governed by >dissipation effects on a surface layer covering the creepage path. The >properties of that layer are ruled by pollution degree and material >group (CTI-value) and possible other factors left out in IEC 61010. As >dissipation is linear with working voltage RMS values, its RMS value >that need to be taken into account for calculating creepage values. I don't think that dissipation necessarily causes, or even correlates with, the growth of a conductive layer on an insulator. Electrochemical processes are driven directly by voltage, not heat. Because of the difficulty of predicting such effects, since they depend on the particular environment, it is *prudent* to base creepage distance requirements on peak voltage, especially as this often presents no particular difficulty. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
