I suggest you apply self-induction with low parallel capacity such as ferrites before any clamping device. Standard varistors do perform self induction in series with the clamping part. The source impedance of the EFT pulse is 50 Ohm. If your low impedance path to ground is 1 Ohm inductive still 40 volts reside. I can assure you that 1 Ohm to ground sereis impedance at this frequency is NOT an easy target.
So first increase the impedance of the EFT pulse as high as physically possible (200-300 Ohms) in the incoming cable/wire and then lead to ground using a low inductace capacitor and varistor. If no impedance is possible use faster devices such as transil (semiconductor) preferably in SMD version to reduce series impedance. Possibly your equipment don't need that much decoupling; just give it a try. uP equipment may be very hard to decouple. Note that relay's and optocouplers are virtually transparent to this pulse... Potential free relay contact outputs are often overlooked. I decoupled thyristor lamp solid state relays using ferrites last year. I needed 4 big ones in series to stop the thyristor from igniting. Need I mention that varistors could not be applied here ? Regards, Gert Gremmen, (Ing) ce-test, qualified testing =============================================== Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ =============================================== >>-----Original Message----- >>From: [email protected] >>[mailto:[email protected]]On Behalf Of >>[email protected] >>Sent: Wednesday, December 12, 2001 9:51 PM >>To: [email protected] >>Subject: Components to suppress fast transient / bursts >> >> >> >>Hi all, >> >>I do not have any experience with components which could suppress a 2kV >>(5ns/50ns) electrical fast transient (Burst). >> >>Anybody in the group who could come up with some suggestions ? >> >>Best regards >>Amund Westin,Oslo/Norway >> >> >> >>------------------------------------------- >>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: >> Michael Garretson: [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: >> No longer online until our new server is brought online and >>the old messages are imported into the new server. >> >>
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