Bruce, There are two answers to this question. No, you can just rate it at -48Vdc which should be good for the US but is questionable in the EU at this point. At -48Vdc (and even during charging @ 60V peak), it is a SELV circuit. Some companies label for the charging voltages, but this should be unnecessary due to the SELV reasons above. (and labeling at -60V may cause you problems due to the ±% that you may be held to by some NRTL's or NRTL engineers. They MIGHT say you exceed the SELV range. Why risk it?)
OR If you want to ship to Europe, the nominal voltage can be -60Vdc. Here it gets tricky as charging voltages are typically 72Vdc. Most NRTL's testing to the new UL60950 will treat DC input voltages at these levels as TNV-2, which is a lot better for design reasons than treating your input circuit as a hazardous voltage circuit. If shipping to Europe, it may also help to leave your label rating at (range maximum) -60Vdc and evaluate for TNV-2 inputs anyway. There may be some loopholes to allow reduced/eliminated production line testing (which is never a bad thing - realistically for this type of application anyway) and you still proved your system safe at TNV-2 level DC input voltages. This all could depend on your NRTL of course (and possibly your engineer within the NRTL). I have also heard of people leaving the rating at -48Vdc and selling it to Europe anyway. I don't fully understand the ethics or legality involved, but the real world input voltages are low enough that they are unlikely enough to cause a safety issue so some European telcos will install the -48V rated equipment anyway as long as they determine it will work reliably in their networks. AS A DISCLAIMER, I DO NOT ADVOCATE THIS PATH, I just wanted to throw it in as an FYI. Hope this helps and does not confuse the issue too much, Dave Heald > "Bruce Touzel (EUD)" wrote: > > Does 48Vdc powered telecom equipment need to have a min and max input > rating ? > > I have heard of 60Vdc max input, maybe because of charging voltage can > peak to this level, or maybe because some countries operate at this > level ? > > thanks > Bruce > > Ericsson Datacom Inc. > IP Network Edge & Access (IPNEA) > 70 Castilian Drive > Santa Barbara, CA > Phone/cell (805) 562-6571 > Fax (805) 685-4465 > bruce.tou...@ericsson.com > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
