Thanks all, for your point(s) of view and 2-cents. Resuming my conclusions:
- Creepage cannot be shorter than clearance. I think that is clear to most of us. - Clearance is essentially based on peak voltage stressing an specific insulator. Even short time transients may breakdown insufficient clearance. No news here. - 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. This essential long time process (may be months to several years) answers also my question on the 3Hz RMS Working voltage. Any AC voltage with a period shorter than months (??!) need to be evaluated as RMS. A simple RMS voltmeter is not Low frequency enough to correctly calculate the RMS values at low frequencies. A data logger or deep memory oscilloscope is the right instrument here. Any comments ? Regards, Ing. Gert Gremmen, BSc g.grem...@cetest.nl 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: ri...@bendbroadband.com [mailto:ri...@bendbroadband.com] Verzonden: Monday, May 12, 2014 11:04 PM Aan: ce-test, qualified testing bv - Gert Gremmen CC: EMC-PSTC@LISTSERV.IEEE.ORG; ton...@europe.com; oconne...@tamuracorp.com; doug...@gmail.com Onderwerp: Re: [PSES] Creepage and RMS I don't have 664 with me, but I think you will find a rule that a creepage distance cannot be smaller than the associated clearance. That sets the minimum creepage distance. (A clearance is based on peak voltage.) At frequencies above 30 kHz, clearance requirements are less than at lower frequencies because there isn't enough time to ionize the air before the voltage changes polarity. Flore Chiang gave a paper on this phenomenon at one of the PSES symposia. rms is specified for creepage distances because the power is dissipated in the pollution that is an almost inherent part of a creepage distance, thus creating micro-arcs and tracking. Creepage distance requirements are always equal to or larger than clearances. (You can't have a creepage without an associated clearance!) Rich ----- Original Message ----- From: "ce-test, qualified testing bv - Gert Gremmen" <g.grem...@cetest.nl> Date: Monday, May 12, 2014 7:20 am Subject: [PSES] Creepage and RMS > I have a question on creepage distances. > A product creates a saw tooth High voltage of 2000 Vpeak The VRMS > measured on the scope on a full period equals 1120 V > > Creepage is based on the RMS value of the voltage so is based on 1120 > V. > > Now the frequency of the sawtooth is 3 Hz. > Should I still consider the RMS value, and at what frequency should I > consider this as a DC value in regard to creepage.... > > Anyone aware of the IEC 60664 standard in respect to low frequency > signals ?? > > > > Regards, > > Ing. Gert Gremmen, BSc > > > > > P Before printing, think about the environment. > > - > ---------------------------------------------------------------- > 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 <emcp...@radiusnorth.net> Mike Cantwell > <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher: <j.bac...@ieee.org> > David Heald: <dhe...@gmail.com> > - ---------------------------------------------------------------- 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
