Hi Folks I see and "hear" what Tania has said, but - from our own experience in developing radio products for the military market - I do not agree that "straight" UL1950/IEC60950/EN60950 compliance is adequate for applications outside the "office environment" envisaged in the basic standard.
ENVIRONMENT Many military applications involve extreme environmental conditions - notably high levels of shock, vibration, temperature and/or humidity - which are typically specified by the customer at the time of tendering/ordering. These conditions can substantially damage equipment and make it unsafe. We subjected a (supposedly) EN60950 computer PSU to vibration testing representative of our required environment and most of the smoothing capacitors fell off the PCB's, and contact between a transistor heatsink and another component generated a lot of aluminium swarf which went "everywhere". Either of these conditions could have (but did'nt actually!!) causedserious primary-to-secondary short-circuits! Cl 1.2 of the 60950 standard allows equipment for other environmental conditions to be qualified to this standard, and so I believe that products must still meet the full requirements of the standard AFTER all aspects of the appropriate environmental-withstand tests have been applied. COMPONENT SPECIFICATIONS Many standard IEC/EN/UL safety components are not suitable for extreme military environments - e.g. 60320 appliance connectors, and many flexible mains cables - as they have neither the temperature range nor the environmental withstand capabilities. You then get into a difficult situation on qualification of such components for extreme environments, or the equally difficult situation of finding "military" components which meet the requirements of 60950 - especially in respect of Creepage and Clearance, and materials flammability. FAULT AND ABNORMAL CONDITIONS I believe that the concept of separate application of a single fault con dition OR a serious misuse condition is not appropriate to such equipment, which will often be operated in poor conditions by personnel under considerable strain. Therefore, I think that any relevant conditions of both types should be applied simultaneously. For example (one we have seen ourselves), a battery charger for external batteries could be tested with an internal component fault which disables charging control and the fitting of a faulty battery will absorb all the charge supplied. This is valid since rechargeable batteries will never be thrown away until it is proven that they cannot be charged - but you do not want a safety hazard caused by overheating inside the charger nor explosion of the battery due to heat and/or gassing! Conversely, most military personnel receive better training, so maybe you can substitute "good training" and/or labelling requirements for some 60950 secondary safety protection requirements - after all this is what often happens in industrial situations where people have to, and are allowed to, routinely perform tasks which are deemed too dangerous for Joe Public. GENERAL In view of the above, I think this is situation where we need to develop a set of additional criteria for military applications - and I would be happy to cooperate with anybody with similar views so that we can have some sort of concensus approach to this real life problem. John Allen Racal Defence Electronics Bracknell UK. ---------- From: Grant, Tania (Tania)[SMTP:[email protected]] Sent: 02 August 2000 17:55 To: Liste emc-pstc; 'Joel Mandel' Subject: RE: EN60950 Military standard equivalent Joe, UL 1950, 3rd edition, has been adopted by the Department of Defense on December 21, 1994. That takes care of the US military. Don't know anything about the rest of the world. Tania Grant, [email protected] <mailto:[email protected]> Lucent Technologies, Intelligent Network Unit Messaging Solutions Group ---------- From: Joel Mandel [SMTP:[email protected]] Sent: Wednesday, August 02, 2000 3:10 AM To: Liste emc-pstc Subject: EN60950 Military standard equivalent Hi All I am looking for a safety standard such as EN60950 for the Military Industry. Thanks Joel Mandel Compliance ADC Teledata ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
