Our company sells ITE systems that are housed in commerial 19" racks. The system is designed to be fault tolerant and redundant, so each rack has two AC mains cords.
We do our own EMI certification testing (we're an accreditted lab), and our typical EUT consists of two of these rack, so there are 4 AC Mains cords to test, which we connect to 4 LISNs. A modified version of this system is now in the works, where the dual AC mains cords are replaced by multiple cords (with lower current per cord). The design now would have 10 AC mains cords out of one rack, and 8 from the other. This means the two rack EUT would have 18 AC Mains cords to test. In a perfect world, where cost were no object, we would have 18 LISNs, since this is the most efficient for testing -- set it up once, and test everything. Our question is how to place a relatively large number of LISNs and satisfy the standards' requirement of the 80cm spacing of the EUT and LISN. Specifically: 1) Are we allowed to place LISNs around all sides of the EUT, maintaining the 80cm spacing (i.e. have LISNs at the front face of the EUT, and run the mains cord from the back to the LISN)? 2) Are we allowed to stack LISNs on top of each other, as long as the LISN is bonded to the ground plane? Since we have to test each cord in turn, we could reduce the number of LISNs by combining a number of the cords not currently being tested through a second (or third) LISN. The downside of this is having to re-plug the cords after each cord is tested, which requires shutting the system down and restarting, which is a non-trivial task (and takes longer than it does to test one cord). John D. Flavin Teradata TCP Engineering 17095 Via del Campo San Diego, CA 92127 john.fla...@teradata.com V: (858) 485-3874 F: (213) 337-5432 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
