Hi Donald:
A VDR is taken as a device that is likely to fail. If the VDR is connected between mains and the protective earthing system, then the PE system must be considered reliable, that is, equivalent to a reinforced safeguard. Ever since the days of 2-wire plugs and sockets, grounding by means of a domestic plug and socket has not been considered reliable (because you could not predict whether the installation was 2-wire or 2-wire plus ground). In order to have a reliable ground, the ground construction must be permanent or equivalent. (Equivalent is taken as by means of industrial- grade plug and socket schemes.) 1.5.9.4 specifies the equivalent grounding schemes. Yes, you are correct in that a VDR is not permitted to be connected to earth (ground) in pluggable equipment type A. Best wishes for a Merry Christmas, Richard Nute Product Safety Consultant San Diego On 12/14/2010 14:20, Donald McElheran wrote: > All: > > Under clause 1.5.9.4 "Bridging of basic insulation by a VDR" in the > latest version of 60950-1 > > Paragraph two: > > "Equipment with such a VDR bridging insulation shall be one of the > following: > > - equipment that has the provision for a permanently > connected PROTECTIVE EARTHING CONNECTOR and is provided with > instructions for the installation of that conductor. > > > This requirement appears to rule out the use of power supplies making > use of earthed VDRs in their primary circuits, if used in "Pluggable > Equipment Type A" if a separate earthing terminal is not provided. > > Could anyone confirm that this interpretion is correct and wether this > was the intent of the committee. > > Donald McElheran > Product Compliance Specialist > Ross Video | Live Production Technology > www.rossvideo.com > +1 (613) 652-4886 > - ---------------------------------------------------------------- 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://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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
