Hi Jim: The 0.25 mA value in IEC 60950 came from UL's interpretation of Class II. Instead of a measure of a value of current which could pass through the body, it is a measure of the "quality" of the double insulation. The reasoning goes like this: If the capacitance across basic insulation yields 0.5 mA, then the capacitance across double insulation (two basics in series) yields 0.25 mA. Despite my protests (I was at the meeting where this was decided), this reasoning prevailed. So now you must design reinforced insulation as well as double insulation for 0.25 mA. UL carried this concept to IEC 60950. Regards, Richard Nute Product Safety Consultant San Diego
From: [email protected] [mailto:[email protected]] On Behalf Of Lyons, Jim Sent: Thursday, March 27, 2008 9:02 AM To: [email protected] Subject: RE: CISPR EN IEC Standards for Set Top Box One issue would be the touch current allowed for Class II products. Under IEC 60065 it is 0.5 mA, and under IEC 60950 it is 0.25 mA. I would be interested in hearing what others think about that. Is the touch current requirement of IEC 60950 unnecessarily severe? Jim Lyons Manager - Product Compliance GTECH Corp. - ---------------------------------------------------------------- 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
