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 < > 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) <http://www.ieee-pses.org/list.html> > 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> > - ---------------------------------------------------------------- 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>
