Hi Aboo, According to Table 1A of IEC/UL 60950-1 2nd Ed, a TNV-1 circuit is basically considered to be an SELV circuit that is also subject to the effects of the intended environment (overvoltages). The effects of those overvoltages should then be controlled by the applied surge suppression device(s) for the intended circuits.
Since the transient nature of the environment should remain relatively unchanged and the equipment is directly affected by the environment, use of surge suppressors should not change the circuit class. This is because such devices cannot eliminate or alter an environment's expected transient and over-voltage/current conditions. Surge suppressors are merely a means of circuit protection from those conditions and only minimize overvoltage or overcurrent effects in the circuits that they protect depending on the type of surge suppressor used and where they're connected. Also consider single fault conditions when/where the surge suppressor would fail. Would the voltage limits of 6.1 of IEC/UL 60950-22 be exceeded under these conditions? IHTH. Best regards, Ron Pickard [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of aboo, chang Sent: Tuesday, October 27, 2009 12:33 AM To: [email protected] Subject: DC power supply protector(IEC60950-1/-22) Dear expert, Our products is outdoor IT Equipment, powered by DC mains. So, normailly the DC input should be considered as TNV-1 circuit. However, can I use surge suppressor to mininize the overvoltage and treat the DC power input as SELV circuit? Thanks. Regards, Aboo. - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
