My advice would be to ask the guy concerned to find out the required information to enable him to calculate how much energy he might have to contain and then dissipate, both under 'normal' and under 'fault' conditions (i.e. if his proposed circuit or something upstream of it suffered a component failure).
My gut reaction is that, even if he can find the information which allows him to produce a reliable figure for this (non-trivial in itself), the number will be high enough that the reasons why this is not a good idea will become obvious. If I'm wrong, well maybe it's an idea worth considering after all. Nick. At 12:25 pm -0400 5/10/06, [email protected] wrote: >Gentlemen, > >I need your collective memory. > >I have an engineer that wishes to design a protection mechanism to apply a >short circuit across the mains in order to open a protection device >upstream to stop an over-heating fault. The protection device would be in >the product, we are not talking about depending on the protection in the >service panel. I will not let them go there. > >I remember somewhere in the past that one of the standards, or perhaps a >country deviation, specifically forbid shorting the mains as a means of >protection but I cannot find it. I think it is from the era when we were >using IEC 380 or 435 and UL 478 but I am not sure. > >Can someone out there point me to the standard and clause? or perhaps the >deviation or an OSM decision? > >I am looking for all of the arguments against this practice I can pull >together because I do not feel it is sound. It is one thing to crowbar the >output of a power supply to protect an expensive logic board from a power >supply over-voltage failure. It is quite another to short the mains input. > >Many thanks, > >Gregory H. McClure >Lexmark Product Safety >859 232 3240 office >859 232 6882 fax > >Confidentiality Notice: >This e-mail message, including any attachment, is for the sole use of the >intended recipient(s) and may contain confidential information. Any >unauthorized review, use, disclosure or distribution is strictly >prohibited. If you are not the intended recipient, please contact the >sender, by e-mail, and destroy all copies of the original message. > >- >---------------------------------------------------------------- >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 - 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 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
