In a message dated 8/31/00, Matt Aschenberg writes: > The fast transient has a ringing (underdamped) wave form. Our primary > concern is to protect the modem against lightening surges. We currently test > to 6kV underdamped and overdamped.
Hi Matt: If your primary concern is lightning immunity, you should probably refer to some industry standards that address this specific topic. In most cases the peak voltage of the surge is limited to less than 1500 volts by the primary protector located where the cable enters the building. However, the peak currents can reach 100 amps, and the total durations can reach 1000 uS. In other words, there is still a lot of energy to deal with. You do not mention the equipment you are using to generate the surges, but if it was not designed specifically for simulating lightning surges, it probably does not generate enough energy to accurately simulate lightning. Two references that describe recommended immunity tests for lightning are ITU-T K.21 and Bellcore/Telcordia GR 1089-CORE. When you develop your lightning protection scheme for the modem, keep in mind that the same circuit must also meet the power cross requirements in UL 1950 (if the product will be used in the North America). You will find that the UL 1950 compliance and lightning immunity are somewhat at odds with each other, so it takes a well thought out design to perform well for both tests. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. http://www.randolph-telecom.com ------------------------------------------- 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]
