Folks, EN 60950-1 defines the requirements for SELV as well as many other requirements. SELV is required under certain conditions as defined and where it's not required it's not needed. EN 60950-1 does not state that all control circuits must be SELV. Therefore all control circuits need not be SELV and it cannot be assumed that all control voltages in an EN 60950-1 machine are SELV.
DC power supply manufacturers routinely certify and claim compliance to EN 60950-1. However, I have only seen a few power supply data sheets explicitly claiming SELV compliance. In fact, I have reviewed several EN 60950-1 test reports for various power supplies (not claiming SELV compliance) and the test results for the SELV clauses are week or actually show non-compliance. For example, component single fault testing for over voltage was insufficient. In some cases power supplies rated for nominal voltage meeting SELV requirements (for example 48VDC) could be adjusted for an output above SELV ratings or the fault testing generated output voltages above SELV requirements (60VDC for longer than 200 ms). In some cases the power supply data sheets will even list EN 60950-1 compliance for supplies with a rated output voltage range above SELV, for example 45-62 VDC. Therefore my contention is it cannot be assumed that a power supply listed as EN 60950-1 compliant on a manu! facturer's data sheet is also SELV compliant unless explicitly stated so or proven in the test report results. I have run across many folks and some CE Machinery Directive compliance reports stating/assuming SELV compliance strictly due to power supplies being certified to EN 60950-1 (without any specific SELV claim). In other words EN 60950-1 == SELV. I'm wondering what other folks opinions are on this? Does anyone know of any supporting articles/guidelines etc. clarifying this? David P. Nyffenegger, PMP, SM-IEEE Product Development Manager - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
