I found this in UL 60950, clause 1.5.9.1: -- quote --- If a surge suppressor is used in a PRIMARY CIRCUIT, it shall be a VDR and it shall comply with Annex Q. NOTE 1 A VDR is sometimes referred to as a varistor or a metal oxide varistor (MOV). Devices such as gas discharge tubes, carbon blocks and semiconductor devices with non-linear voltage/current characteristics are not considered as VDRs in this standard. --- end quote ---
This sounds like it prevents the use of VDR/gas discharge tube combinations to limit primary-to-earth line surges, or gas discharge tubes in the primary completely. Is this correct? I'll bet the gas tube companies are having heartburn over this. Pat Lawler EMC Engineer SL Power Electronics Corp. ri...@ieee.org wrote on 12/15/2010 12:05:18 PM: > On 12/15/2010 11:41, Kunde, Brian wrote: > > Does it make VDRs safer to use them in series with a gas-tube like some > > do with Varistors? > Hi Brian: > > Yes. > Today, this is the trend among manufacturers that > want to use a VDR between mains and earth. > And, TC108 is still trying to sort out the requirements > for both devices in such a circuit. > > Best wishes for a Merry Christmas, > 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://product-compliance.oc.ieee.org/ > 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 <emcp...@radiusnorth.net> > 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://product-compliance.oc.ieee.org/ 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
