In a message dated 1/21/00, John Boucher writes: > What I'm really wrestling with is whether we need to be concerned about power > line cross / induction issues outside of North America. >
John: I too have heard the argument that AC mains wiring outside of North America is "different," and that as a result, power cross is less of a risk outside North America. I'm not sure that I believe this. Even in North America, power cross and induction at levels that present an actual safety risk are extremely rare events. My impression is that the people developing safety standards for North America were perhaps the first to identify power cross as a possible risk, and the first to include power cross requirements in their standards. Even so, there was considerable internal debate about whether power cross and induction presented enough of a safety risk to justify inclusion in the safety standards. I have heard that at the IEC level, many member countries have been skeptical about the actual severity of the power cross risk, and have been reluctant to include power cross requirements in IEC standards such as IEC 950. Some observers think this may change in the future. I would note that the 1996 version of the ITU K.20 requirements now contains several power cross tests. In addition, the new EN 300 386 (for telecom network equipment) includes several power cross tests. This indicates that there is now at least some acceptance at the international level of the risk of power cross and induction. My suggestion would be to use your North American line interface design (including UL 1950 power cross compliance) for your international applications as well. This will eliminate any doubt about whether you have chosen the proper path for international applications. A properly executed line interface design will add very little cost to the interface, so the cost penalty for including power cross protection in your international version should be small (I have seen some designs that were quite expensive, but they don't have to be. There are several ways to comply with the requirements, and some designs are much better than others). An added benefit of using the same line interface in all countries is that it increases your unit volumes for components, and it reduces the number of different line cards that must be manufactured and supported. These savings can help to offset the small added cost for power cross protection in the international applications. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
