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Hi, Across the secondary winding of a DC/DC converter transformer powering an un-earthed SELV load, we have a 75V peak 350KHz square wave at 75VDC input. One side of the winding is connected to the un-earthed SELV ground and the other side is switched by transistors and goes through an inductor to produce an SELV power voltage. We also have a snubber circuit with a capacitor charged at about 90VDC and connected to the same SELV ground. If there is no risk the SELV output would exceed SELV limits in the event the insulation would fail across components, do we still need Basic insulation across the components and between the components and the SELV ground or can we apply Functional insulation ? If we provide the required category of insulation could we still run into certification issues because we have hazardous voltages not "truly" insulated from the SELV power output due to active components bridging the insulation ? If yes, could a reliable crow-bar, such as a TVS diode across the output, solve the issue ? Thanks, Eric =================================== Éric Meunier Designer EMC/Environmental E-mail: [email protected] Kontron Canada Inc. 616, rue Curé-Boivin Boisbriand, Québec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [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: http://www.ieeecommunities.org/emc-pstc
