Mr. Nute's response is significant and is worthy of re-emphasis.
And Mr. Woodgate answered this same question to Mr. Nyffenegger previously: " The power supply as a whole cannot claim that unless ALL its outputs meet the SELV requirements. But it does meet the requirements for safety isolation, so those outputs that meet the voltage requirements are SELV." SELV, TNVx, LPS, LCC, etc are specific ratings that would be indicated in the Conditions of Acceptability in both the test certification document required to bear a CAB's logo and the respective CB report. And as many power supplies are components, the report will be necessarily incomplete; and only the assessment in the end-use construction can provide a complete report. Per Mr. Nute, other than simple flyback converters, most component SMPS are too complex to be evaluated by other than an assessment directed by the original manufacturer (in last 15 years, have encountered only three agency engineers capable of a complete and independent assessment of SMPS). There is never any logical reason to assume a 'certified' component power supply will meet any specific ratings unless stated in a CAB's report. Brian -----Original Message----- From: Richard Nute [mailto:ri...@ieee.org] Sent: Monday, January 19, 2015 12:55 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] SELV rated power supplies Hi Dave: EN60950-1 is not equal to SELV. Certifications and reports do not necessarily indicate outputs are SELV, although careful reading of the test results can conclude that the outputs are SELV or not. Not all outputs of EN60950-1 power supplies are SELV and need not be. The power supplies are nevertheless EN60950-1 power supplies. The requirement for SELV is whether or not the circuit is accessible. Accessible circuits must be SELV. To perform a single-fault test, one must understand how the circuits operate, and what faults could cause the output to possibly exceed SELV limits. In today's power supply topology, such circuit analysis is not necessarily straight-forward. Your statement "Therefore my contention is it cannot be assumed that a power supply listed as EN 60950-1 compliant on a manufacturer's data sheet is also SELV compliant unless explicitly stated so or proven in the test report results." is correct. Best regards, Rich - ---------------------------------------------------------------- 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>
