I read in !emc-pstc that Rich Nute <[email protected]> wrote (in <[email protected]>) about 'How do I do this test?' on Mon, 8 Dec 2003: > > > >Hi John: > > >> For professional audio, it's common to design to Class II requirements >> and then add an earthed screen in the mains or SMPS isolating >> transformer, and a user option to connect signal common to the PEC or >> not. > >This seems to bring us full circle, back to >the original topic, that of Class I and Class >II insulations in parallel. > >I would presume that professional audio uses >Class II requirements between the mains and the >earthed screen, i.e., the connection to the PEC >is not a safegurd function?
It varies: the earthed screen has often been regarded as a safeguard, with basic insulation to the primary circuit. More recently, the realization that the screen must meet the fault current requirement may have changed the thinking on this subject. The screen also has a functional role in reducing mains-borne conducted interference. > >IEC 60335 3rd defines Class OI as a basic- >insulated product with a functional earth >terminal for optional, non-safeguard connection >to earth. Classes O and OI are not permitted now in almost all European countries. > >If the product is Class II, and is provided >with a functional earth terminal for optional >non-safeguard connection to earth, is it then >a Class II-I? :-) > AFAIK, that term has not been used. Class II is not allowed to have any sort of earth terminal by some safety standards. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
