Scott:
I didn’t want to drop names about vendors, but Vicor has been my favorite for smart power supplies since I crashed into the same problem (on a smart bomb system around 1990) that you are now seeing. Vicor made commercial and MIL grade units, and they even offered an auxiliary module (called maybe a filter or power factor correction module) that met Army ground RE102 limits. Unfortunately, this auxiliary module was almost the same size as the whole converter, and you needed to mount both modules physically close to each other. I would imagine that other vendors have addressed this, and maybe somebody now puts it all into one brick. The point is, you and your client are probably not power supply design experts, so trying to find fixes for this power supply problem issue is likely not going to be as cost-efficient as getting a more costly yet MIL compliant power supply from your vendor (who really IS a power supply expert). Whenever I had the opportunity (and when designers would listen), I would suggest that the system designers get a real sample of the power modules from each of the vendors that they might be considering, and I would give them all a quick RE102 comparison. It was instructive (for all of us) to see how some modules would just barely squeek by the limit, and how others had much lower emissions. The system designers could then use this info to add to their overall design risk analysis. (It was also a good time to discuss the importance of a dB, as in “hey, this brick is a full 1.8 dB under the limit at the 5th harmonic, so we don’t have any worries about this model!”) BTW, on the system I mentioned, the system designer paralleled about 10 identical Vicor power supplies on a single power source bus. Then, he used each power supply enable logic line to only turn on whatever power supply was needed at any given moment. This considerably reduced power consumption, and eliminated relays or power switching semiconductors. I was really impressed by elegant trick (although sometimes I’m easily impressed). Ed Price WB6WSN Chula Vista, CA USA From: S Drysdale [mailto:[email protected]] Sent: Thursday, February 25, 2016 6:58 AM To: [email protected] Subject: Re: [PSES] Recommendations for DC-DC converter Hi Ed, I believe you hit the nail on the head, figuratively. The problem is the use of a commercial DC-DC converter that is not meeting the required specification. The product and components must fit in a tight space, and spacing is extremely tight, so there is limitations on the external components we can add to filter this. This is the main problem we are running into with the current DC-DC converter, and I think a different DC-DC converter may require substantially less external filtering, or hopefully none at all. I have found gaia and vicor power imply some degree MIL-STD compliance, but I was hoping for manufacturer or product recommendations from those familiar with the concern. Best Regards, Scott Drysdale, OOO - Own Opinions Only http://ca.linkedin.com/in/scottdrysdale On Wed, Feb 24, 2016 at 4:22 PM, Ed Price <[email protected]> wrote: Scott: First, can we assume that the converter itself has already been successfully tested to RE102? If you are trying to use a commercial converter in a MIL environment, you may be starting at a big disadvantage. Some converter vendors offer an auxiliary active filter module, so get the vendor involved in your problem. The RE problem is probably not originating from radiation directly from the converter case, but from radiation from cabling connected to the converter. You may be able to decrease common mode currents with external ferrites or inductance, twisted pair power feeds may help and you should carefully review the mounting of the converter to the platform frame. Ed Price WB6WSN Chula Vista, CA USA From: S Drysdale [mailto:[email protected]] Sent: Wednesday, February 24, 2016 11:41 AM To: [email protected] Subject: [PSES] Recommendations for DC-DC converter All, My client has a very tight imposed limit for radiated emissions. Let's assume MIL-STD RE102 army ground. We are exceeding emissions caused by the DC-DC converter. Shielding is difficult in this application, and something we would like to avoid. Space requirements are an issue, and we think it may be easier to switch the module altogether. Input 48Vdc, Output is 12Vdc, 1.7A (or ~20W). Size is somewhat important, where smaller is better, but meeting this radiated emission limit is essential. Any recommendations? Best Regards, Scott Drysdale https://www.linkedin.com/in/scottdrysdale OOO - Own Opinions Only - ---------------------------------------------------------------- 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) <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]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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) <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]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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) <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]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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]>
