Hi Amund, I like to use relatively high power MOV's at the supply input (AC or DC), voltage appropriate to the incoming supply and energy rating appropriate to the protection energy required, bearing in mind possible progressive deterioration. Then I also use lower power hence much smaller transobs ‘distributed’ around the system, i.e. at supplies to key components on a PCB (IC’s usually) or other DC powered modules, voltage rated appropriate to the local supply voltage which is (generally) lower than the incoming supply.These help with transients coupled in by means other than the supply wires. The latter has proven most valuable additional protection against FTB and ESD induced transient interference not afforded by protection at the incoming supply. It may seem overly belt-and-braces but it’s a lot easier to remove protection than add it later – This strategy has proven it’s worth on more than 1 occasion. I used Transobs on PCB’s for the first time back in the mid 80’s to ‘manage’ ESD induced noise. Don’t think I’ve designed anything without them since. Hope this helps. Tony
From: Amund Westin <[email protected]> To: [email protected] Sent: Mon, Oct 12, 2009 8:34 pm Subject: [PSES] Surge protection components - DC line 24VDC port shall be protected against 1kV (line-earth 10ohm) and 500V (line-line 2ohm). (ref.IEC61000-4-5 8/20us pulse) Should I go for MOVs or tranzorbs? I have good experience with MOVs on 230VAC ports, but have not done any work on DC ports. #Amund - 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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.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]>
