Re: [PSES] IEC/ANSI/UL/CSA 60950-1 ed.2 Mains Vrms vs Vpeak

[Doug Powell]

Good point, I'll take a look this morning. Thanks! Doug From: ibm...@gmail.com Sent: March 29, 2017 7:43 PM To: doug...@gmail.com Cc: EMC-PSTC@listserv.ieee.org Subject: Re: [PSES] IEC/ANSI/UL/CSA 60950-1 ed.2 Mains Vrms vs Vpeak Hi Doug; Have you taken a look at IEC 60664 to see if has a similar statement or provides any clarification?  Maybe what you're seeing is just a mistake in 60950-1, 2nd ed... -Ken On Wed, Mar 29, 2017 at 8:48 PM, Doug Powell <doug...@gmail.com> wrote: All, I am reviewing the requirements of "2.10.3.3 Clearances in primary circuits" and it seems interesting to me that the math is off by just a little bit.  In particular "For an AC MAINS SUPPLY not exceeding 300 V r.m.s. (420 V peak)". When in actuality the calculated peak of 300 Vrms is 424 Vpeak.  Using three significant digits instead of two.  This value is important to spacings determination in that it invokes using tables 2K plus 2L instead of table 2K alone.  I checked the Edition 2 of IEC, ANSI/UL and CSA standards and they all have the same statement.  Edition 1 of IEC 60950-1 does not include this value within parenthesis which tells me it was probably added as a clarification by the committee in Edition 2. I am one to build excel-based spacings calculators and this has changed the math somewhat, rounding up to the nearest 10 Volts =IF(10*ROUNDUP(Vrms*SQRT(2)/10,0)>420,"Tables 2K + 2L","Table 2K") instead of using =IF(Vrms*SQRT(2))>424,"Tables 2K & 2L","Table 2K") (Note: use of =MROUND() could potentially round down and not up) In several other sections of the standard another pair of voltages appear together in at least 8 locations and are rendered "42,4 V peak, or 60 V d.c"; which is correct for three significant digits.  I know the consequences are probably minimal and it has raised my curiosity as to why this happened. Was anyone in this forum present during this part of the revision discussions and can shed some light? thanks Doug -- Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- 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 &LT;emc-p...@ieee.org&GT; 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 &LT;sdoug...@ieee.org&GT; Mike Cantwell &LT;mcantw...@ieee.org&GT; For policy questions, send mail to: Jim Bacher &LT;j.bac...@ieee.org&GT; David Heald &LT;dhe...@gmail.com&GT; - ---------------------------------------------------------------- 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>