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In article <[email protected]>, Peter L. Tarver <[email protected]> writes >There you have it. You may dice it coarsely of finely, but the above >represents a *National or Group Difference* and should be properly >documented in both the EN version of any and all effected standards Consider that it takes time to amend a standard (a minimum of 3 years, normally). I am not involved to any significant extent with the maintenance of EN 60950, but > and >in the CB Bulletin. I have no idea why it wasn't in the CB Bulletin. Possibly just human error. >Simply because factions within the EU chose to >refer to this rose by another name and claim it's existence is the >result of another process (ie, through CENELEC and its membership), does >not change the ultimate effect and amounts to rationalization. I'm not quite sure what you mean by that. There is no 'faction'; the rejection of MOVs to earth/ground is based on the technically-sound fact that they are liable to fail short-circuit, and the chance of this happening was considered by some, but not all experts, to be not remote enough to disregard. Such a short-circuit constitutes a prospective high-current fault, which can give rise to chain-reaction effects causing damage to the equipment and to other equipment connected to it. There is an electric shock hazard, although IMHO it is minimal, because the high current tends to imply a low-impedance earth connection (although the short-circuit failure doesn't). There is a further potential hazard in the case of a low-impedance earth connection - that the MOV may violently disrupt as a result of the high fault current, creating a hazard from metal vapour and flying particles. I believe that MOVs to ground are not allowed in one or more N. American countries. It is certainly unfortunate that in this case, unanimity in Europe at the OSM level was not achieved, but this is not a common occurrence where technical issues are concerned. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
