Rich and Andy - There is an additional reference in 4.3.9 of IEC60950, Second Edition, and applies where certain types of required insulation can be bridged, rather than being limited to just power supply cord conductors (though this could easily have been the origin of the "requirement" [actually, an option in the compliance statements, rather than a requirement]). See also, C.2, for transformers.
In IEC60950, Third Edition, and variants, this additional reference is 4.3.4, under the heading, "securing parts." See also, 3.1.9 and C.2. I note that the reference specific to power supply cords is absent (probably considered redundant, in the new formatted document) in the Third Edition. Regards, Peter L. Tarver, PE [email protected] -----Original Message----- From: Rich Nute [mailto:[email protected]] Sent: Wednesday, September 20, 2000 12:08 AM Hi Andy: > I have been told that either "double crimp" terminals (fast-ons, ring, > spade) must be used for insulated wire, or a secondary method must be used > to secure the wire's insulation near the point of connection. I have not > seen this described in the standards I have read or in the archived emails > on the RCIC database - where should I look? At this point, I don't even > know if this is a UL or a LVD thing. This is a long-standing, traditional, and semi-secret safety requirement. In my experience, it has been applied by both CSA and UL. The requirement is based on the concept that safety must be provided both for normal conditions and in the event of a fault. Where a wire could come loose and bridge a safety insulation, then that wire must have a second mechanical scheme that prevents the wire from bridging the insulation. The requirement is stated in IEC 60950 and its clones in Sub-clause 3.3.4 for power supply cord wires. This same requirement MAY be applied to other wires at hazardous voltage by the many different certification engineers, each of whom has a different reason for doing so. There is a similar requirement for containment of strands of stranded wire. See Sub-clause 3.3.9. You didn't ask what are the secondary methods. Any secondary method that keeps the wire from bridging a safety insulation is generally acceptable. The "double crimp" is acceptable because the first crimp is to the wire, and the second crimp is to the insulation. Two, more-or-less independent fixings. Best regards, Rich
