The breaker, in this case is not used to interrupt current from a branch ckt, but to meet the requirements for LPS limits of a secondary ckt.
Also in this thread, Mr. Nute had stated that safety standards may not be addressing reliability. The problem here might be specific to North American (NEC/CEC) requirements, where the applicable safety standard for an LPS would probably be UL1012, CSA107, and/or CSA220. In addition to the OP, I would also like to know if this is the source for not allowing breakers to meet LPS limits. An LPS, in addition to the requirement to be safe for human contact, must also not be a fire hazard when used in cable trays and industrial wiring conduits that are used for non-mains signals and control voltages. The NEC and CEC specify, somewhat indirectly, what is considered a safe current interrupt device for these conditions. As for 'reliability', can we assume that safety standards such as 60730, 61058, 61015, 60384, etc address the issue of reliability through a min number of cycles, or am I making an invalid comparison of apples to oranges ? Back to the lab to see if anything has melted... luck, Brian From: [email protected] [mailto:[email protected]]On Behalf Of John Woodgate Sent: Thursday, June 19, 2008 9:42 AM To: [email protected] Subject: Re: 60950-1:2006 clause 2.5 - Limited power sources In message <002e01c8d226$d56ba150$c600a8c0@PC323541548743>, dated Thu, 19 Jun 2008, 'Rich Nute' <[email protected]> writes: >Circuit-breakers probably are not operated even 100 cycles during their >lifetime. In order to meet the 60950-1 requirement to disconnect both mains poles because either may be live, a breaker is used as the main power switch, thus saving two fuses. Those breakers are used quite often. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
