=*=*packet mod warning=*=* > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of John > Woodgate > Sent: Monday, January 14, 2008 12:27 PM > To: [email protected] > Subject: Re: Y1 cap info > > In message <[email protected]>, > dated Mon, > 14 Jan 2008, Brian O'Connell <[email protected]> writes: > > >I have not been able to find fundamental construction > information for > >Y1-rated capacitors. > > Obviously, details may be commercially-confidential. But in > principle, > they consist of a metal film/dielectric sandwich, so > designed that if > the dielectric is punctured, the surrounding film evaporates > during the > discharge, thus isolating the puncture and preserving the insulation > resistance minimally degraded.
thanks, very interesting. > >I am also looking for failure mode and reliability info. > > They have to meet the relevant requirements of IEC 60384-14. A question on this std - why do Y1 caps not have to meet the active flammability test, but Y2-rated caps must ? > > > >What I can find, makes me feel neither warm nor fuzzy for > use in Class > >II construction. > > Y-capacitors are basically intended for connection > line-to-earth. Since > Class II products don't have an earth connection, > Y-capacitors are not > used for that purpose in them. So, if you want to connect a > capacitor > from the mains side of a Class II product to the accessible > side, you > have to make sure that the reliability etc. are adequate on a > case-by-case basis. You also need to ensure that touch-current > requirements are met, which severely restricts the maximum value of > capacitance. While our design technically conforms to the requirements of 60950-1, I do not feel 'right' about a single component bridging either primary/secondary, or primary/floating metal in a Class II unit until I can learn more about Y1 cap reliability and typical failure modes, so I have no information for a case-by-case basis. Thanks much, Brian - 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
