Re: [PSES] requirement for spacings

[Douglas Powell]

Bostjan, As Scott mentioned, it is very important to know which end standard is being applied to this product. In addition there are many other factors such as environmental conditions, application, location, etc. If this is truly DC powered, it is entirely possible your spacings will be for secondary circuits and somewhat reduced. Nevertheless wiring, ‎connections, fuses and the like will have to be rated and certified/listed for that voltage.   If you can provide a little more information about the application and end use, we may be able to provide better assistance.   ‎All the best, Doug From: Scott Aldous Sent: Wednesday, September 9, 2015 9:15 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Reply To: Scott Aldous Subject: Re: [PSES] requirement for spacings Hi Bostjan, It's difficult to give detailed guidance without knowing what end standards are being applied, but the general guidance in IEC 60664-1 should be helpful. In general, +30% tolerance on input voltage is outside the assumptions of most (if not all) safety standards. An electrical rating of 560Vdc +30%/-15% doesn't seem to be appropriate and should be expressed as a range instead. The range here is from 476 - 728 Vdc! For example, 600V rated wire would seem to be an acceptable choice for external wiring for the input of a device marked with a 560V input rating, but in this case the input voltage may be able to be significantly higher than 600V for extended periods. A marked rating of 560Vdc would be misleading. If your end standard allows the clearances to be determined based on assumed transient levels, then the nominal input voltage (or voltages) becomes less important for clearances as long as you are able to make an accurate assumption about the transients. The 840Vdc level potentially could be taken as a temporary overvoltage for the purposes of calculation of clearance, again depending on the end product standard. At least one end product standard that I know of, IEC 62109-1, takes both transient overvoltages and temporary overvoltages into account for calculation of clearances. For creepage, at a minimum, I think you would want to base creepage distance requirements on the 728Vdc high end of the input voltage (560Vdc + 30%). Whether or not you should use the 840Vdc level instead may depend on the specifics of the case, such as how frequently this can happen, what controls are in place to ensure that this is reliably the case, etc. Again, the requirements of the end product standard need to be taken into account and will certainly influence your decision. On Wed, Sep 9, 2015 at 4:03 AM, Boštjan Glavič <bostjan.gla...@siq.si> wrote: Dear Experts, Manufacturer specified rated voltage of his product as 560VDC +30%/-15% but input voltage can temporarily reach 840VDC (max 1 min). Do we need to consider 840VDC for determination of required distances? Usually standard requires to consider rated voltage only what is in this case 560VDC (marked on the label). Thank you for your support. Best regards, Bostjan Boštjan Glavič Laboratory of Electronic Engineering Head of Laboratory SIQ Ljubljana, Tržaška cesta 2 SI-1000 Ljubljana, Slovenia T: + 386 (0)1 47 78 265 F: + 386 (0)1 47 78 444 E-Mail: bostjan.gla...@siq.si   - ---------------------------------------------------------------- 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> -- Scott Aldous Compliance Engineer Google 650-253-1994 scottald...@google.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> - ---------------------------------------------------------------- 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>