Charles -
> From: Charles Blackham > Sent: Friday, November 14, 2003 5:54 AM > > I wish to provide a safety barrier between the > User connecting to the 10/100 RJ45 Ethernet port > and the TNV3 circuitry within my unit. > > Can anyone recommend a suitable Ethernet > transformer that is a UL recognised component and > meets the Creepage and clearance distances for > Basic insulation? I'm not aware of any ethernet transformers that provide Basic Insulation, but there may be some. All I can suggest is to try the big players: Midcom, Pulse, Bel Fuse, et al. Each of those mentioned have telephony transformers that meet Basic Insulation requirements. I don't know the innards of your equipment, but it would seem easier to use a barrier at the TNV-3 interface and have the remainder of the product's secondary circuits be SELV. There are circumstances I've come across that don't make this practical (for instance, a large systems) and there are ways around the construction requirement for most markets (certain "Nordics" excluded). > Alternatively, can I use rely on the "through > insulation" breakdown of the enamel insulation > and potting on a bi-filar wound core? Do I just > have to meet the electric strength test, or am I > missing something here? In general, no, you can't rely on this. For Canada and the US, there are some special cases where magnet wire is allowed to provide insulation (not simply isolation) in a TNV-2 or -3 circuit, but I don't think you'll find an ethernet transformer that you can guarantee will meet these requirements. FWIW, there is a proposal in TC108 (108/69/CD) to permit limited use of enameled magnet wire for compliance with TNV-x requirements. I don't know the current status of this document and can not accurately predict (who can?) it's complexion in final for. Good luck. Regards, Peter L. Tarver, PE ptar...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
