Hi Doug:
Typically, any safety isolation barrier specified by UL will involve some or all of the following four parameters: * Hipot test * Creepage distance * Clearance distance * Distance through solid insulation I suggest that you carefully review the UL requirement you want to meet, and determine the specific values you need for the four parameters listed above (for some types of isolation barriers, not all four parameters have specified requirements). The required values for the above parameters will then dictate what sort of transformer construction would allow you to provide the required values. Note that the 1500 VRMS hipot rating on Ethernet transformers does not come from UL. It comes from the IEEEE 802.3 Ethernet standard. In IEEE 802.3, this requirement is just a voltage-withstand test, and there are no corresponding requirements for creepage, clearance, or distance through solid insulation. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) <mailto:[email protected]> [email protected] <http://www.randolph-telecom.com> http://www.randolph-telecom.com From: Doug Powell [mailto:[email protected]] Sent: Monday, November 03, 2014 2:00 PM To: Joe Randolph; [email protected] Subject: Re: [PSES] Network Isolation Transformer Joe, Thanks for this, good information. I will check out that Bourns part. I have an application for a communications channel over pairs of HV wires. Similar to Power Over Ethernet for running a device, but definitely not the same. I've seen that 1500V rating as well, which is a 60 second dielectric test. Looks great for a marketing brochure. If you rearrange the algebra for "typical" hipot calculation you get (1500-1000)/2 or a 250 VAC working voltage, not so great and certainly not UL listed. I could do a fiber optic link but this would be a major change to the product design in order to get transceivers and isolated power on the HV side. In any case this is driven by a UL safety standard and I have virtually no hope of fining a UL listed device so we will likely have to go through all the component qualifications for the application. My last option may be to design a transformer from scratch with fully insulated windings on primary and secondary using UL style wire appropriate for the job. If that is still not enough, encapsulation could be an option. All the best, Doug On 11/3/2014 11:44 AM, Joe Randolph wrote: Hi Doug: That's an unusual set of requirements. Is this a conventional Ethernet transceiver application for twisted-pair, or something different? Any Ethernet transformer that complies with the IEEE 802.3 standard will be rated for 1500 VRMS isolation and should easily meet your 1200 VDC requirement for primary-to-secondary isolation. However, this is just a voltage test and there are no corresponding guarantees for internal creepage, clearance, or distance through solid insulation. So, specifying only the external creepage distance may not be adequate, depending on what particular requirements you are trying to meet. That being said, if your 5.1 mm creepage distance requirement applies primary-to-secondary, most Ethernet transformers put all the primary pins on one side of the package, and all the secondary pins on the other side of the package. For primary-to-secondary creepage distance, there is no need to be concerned with the separation of adjacent pins on the same side of the package. You should be able to achieve your 5.1 mm goal with the side-to-side separation of most Ethernet transformers. One particular Ethernet transformer that was explicitly designed for high primary-to-secondary isolation (5000 VRMS) is the Bourns SM51589PEL. The external primary-to-secondary creepage distance of the package is approximately 10 mm. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) <mailto:[email protected]> [email protected] <http://www.randolph-telecom.com> http://www.randolph-telecom.com From: Doug Powell [mailto:[email protected]] Sent: Monday, November 03, 2014 12:22 PM To: [email protected] <mailto:[email protected]> Subject: [PSES] Network Isolation Transformer All, I am searching for an ethernet isolation transformer that has a PRI to SEC safety isolation rating of at least 1,200 VDC. On top of that a surface mount version is preferred but not essential. I am able to identify several with a manufacture rating high enough but pad-to-pad creepage distance is only about 1.5 mm on the surface of a PCB and I need at least 5.1 mm. I appreciate hearing about any sources you might be able to identify for me. Doug -- Douglas E Powell [email protected] <mailto:[email protected]> Skype: doug.powell52 http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- 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 <[email protected] <mailto:[email protected]> > 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) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected] <mailto:[email protected]> > Mike Cantwell <[email protected] <mailto:[email protected]> > For policy questions, send mail to: Jim Bacher <[email protected] <mailto:[email protected]> > David Heald <[email protected] <mailto:[email protected]> > Thank you, ~Doug -- Douglas E Powell [email protected] <mailto:[email protected]> Skype: doug.powell52 http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
