Richard - Which edition are you referring to? 2.2.1 in EN60950-1 and EN60950, 3rd ed., addresses general requirements for SELV circuits. In these standards, there is also no 2.9.4.anything.
I'll assume for now that it's 2nd ed., through the 4th amendment. 2.9.4.2 refers to thin sheet material and accepting thin sheet material as a valid construction method for Reinforced Insulation, it must be physically protected; hence internal to a mechanical enclosure. This was written into the standard to allow common transformer constructions to meet Reinforced insulation requirements and other 2.9.4.1 states Reinforced Insulation can be 0.4 mm, and is not precluded from being outside the enclosure, *if* it's not subject to mechanical stresses that can deform the insulation at normal operating temperatures (it implies it *can* deform under abnormal operating conditions that lead to abnormal temperatures). [Be sure to pay attention to the Note.] What you've described seems more like a combination of Basic Insulation (the inner, single conductor insulation) and Supplementary Insulation (the jacket). If the cable is outside the enclosure, it should be jacketed for mechanical protection. Jacketed cables offer many thicknesses of jacket such that you could readily find one that has a 0.4 mm thickness (16 mils). Regards, Peter L. Tarver, PE Product Safety Manager Sanmina-SCI Homologation Services San Jose, CA [email protected] > From: [email protected] > > Consider the insulation construction for an > external interconecting cable > connected to secondary hazardous circuits of ITE > (EN60950). Is it > permissible for the reinforced insulation to be > constructed of two layers > (e.g., conductor insulation plus external jacket) > if the total thickness is > at least 0.4 mm? Clause 2.2.1 appears to allow > it; however, clause 2.9.4.2 > appears to indicate that layered insulation can > only be used internally. > > Richard Woods > Sensormatic Electronics > Tyco International ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc 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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
