To simplify; I often saw transformers declared class A pretty simply w/o any record of an independent evaluation or certification. Higher classes are another matter completely. To get a transformer approved for operation above the limits for class A, one needs a separate evaluation. I'll skip detail over which standard or process could be used, simply to assert that you'll need to talk to your NRTL or NB about this... unless the vendor has a class B equivalent. You'll need either: a class B transformer, a new certification for the transformer in use to class B, or some fairly specialized in-product testing and additional safeguards. Any way you take that advice, you're going back to your NRTL or NB... Colorado Brian
---------- Original Message ---------- From: Scott Aldous <00000220f70c299a-dmarc-requ...@ieee.org> To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Transformer insulation class Date: Thu, 19 May 2016 08:22:22 -0700 I assume this is in regard to certification for the US (i.e. NRTL certification). UL 1446 is the standard for insulating material systems (UL category code OBJY2). Interpretation of this particular requirement may vary depending on the agency you are dealing with and the product category for the end product. As the guide card information I linked to indicates, UL generally considers insulation systems rated higher than class A to require evaluation to UL 1446. The rationale is that there are interactions of the materials (including items specific to construction configuration) that come into play, so individual insulation system component ratings are not sufficient information to determine the classification of the whole insulation system. If your product is subject to UL and/or IEC 60950-1, then IEC 60085 is referenced in Annex P.1, and UL 1446 is referenced in Annex P.2. (as an alternate component standard for the US). If you have access to the UL Practical Application Guidelines for UL 60950-1, take a look at P1.5.2-5 Required use of insulation systems other than Class A. This PAG notes that both the IEC and UL standards have statements to the effect that a system class cannot be determined just from the individual materials used. The "OTHER" section of the PAG has the interesting statement that "Most NCBs do not apply IEC 60085 as intended..." On Thu, May 19, 2016 at 7:55 AM, Doug Powell <doug...@gmail.com> wrote: Ian, My personal experience is mainly with custom switch mode transformers, some very high power and intended for use in high temperature ambients. These have been used in European, North American and Asian markets. In every case these transformers have been approved through evaluation within the product or products where they are used. This evaluation included material classes for insulation, thermal and flammability; ‎construction review and finally performance testing within the product itself. In twenty years, I have yet to certify a custom made switch mode transformer as a separate component. That said, I have on a couple of occasions had to get a special evaluation done on some insulating materials, such as ball pressure, hot wire, etc. In these cases, I find it best to have your supplier do these evaluations and pass the certs along to you. It can take months to complete. All the best, Doug -------------- Sent from my smartphone, please excuse the typos.From: McBurney, IanSent: Thursday, May 19, 2016 3:19 AMTo: emc-p...@listserv.ieee.ORGReply To: McBurney, IanSubject: [PSES] Transformer insulation class Hello colleagues. The switch mode transformers we use in our power supplies are specified by the testing agency as insulation class A even though the materials used in the transformer are all rated for 130°C operation. We have asked the agency to up rate the transformer to insulation class B but the say they cannot do this as the transformer would have to be approved as a component. Is this correct? Many thanks in advance. Ian McBurney Design & Compliance Engineer. Allen & Heath Ltd. Kernick Industrial Estate, Penryn, Cornwall. TR10 9LU. UK T: 01326 372070 E: ian.mcbur...@allen-heath.com Allen & Heath Ltd is a registered business in England and Wales, Company number: 4163451. Any views expressed in this email are those of the individual and not necessarily those of the company. - ---------------------------------------------------------------- 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> - ---------------------------------------------------------------- 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> -- Scott AldousCompliance engineergoogle650-253-1994scottald...@google.com- ---------------------------------------------------------------- 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> - ---------------------------------------------------------------- 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>
