Thanks Richard! ---- Richard Nute wrote ----
> > >Hi James: > > > >My answers to your questions: > > > >1. Does 6.7.3 apply for the clearance between the secondary winding and >earth as indicated? > >Yes. > >2. If NO to 1) then what parts should this insulation be between? >3. If YES to 1) then: > >a. what is the safety hazard that is being addressed by applying Basic >insulation values from Table 6 here? > >The standard's assumption is that transient voltages do appear in secondary >circuits. See NOTE following 6.7.3.1. A transient voltage can cause a >clearance or creepage to fail. Solid insulation is required to have >suitable electric strength to withstand the transient voltage. > >b. Why isn't this shown on Figure D.1e) as being required? > >I assume that the figures are either insulation in general, including >clearances (air insulation) or just for solid insulation. > >4. If the working voltage between terminals X and Y in the sketch is >less than the Hazardous Live thresholds in 6.3.1 then it is be permitted to >be present on an Acccessible external terminal, correct? > >Yes. > >5. Earthing either end of this winding will make 6.7.3 redundant, >correct? > >I wouldn't describe the requirement as "redundant." If one end of the >winding is connected to earth, then clearly the clearance and creepage >requirements do not apply to that one terminal. However, the other terminal >still must meet the clearance and creepage requirement. > > > >The standard seems not clear as to whether clearance (air insulation) is >considered as insulation or a separate parameter. > > > >Note that the values for creepage distance are based on rated voltage, not >transient voltage. This is because failure of a creepage is caused by a >long-term voltage. However, physically, a creepage cannot be less than a >clearance. > > > >Good luck, > >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://www.ieee-pses.org/emc-pstc.html > >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: >Mike Cantwell <mcantw...@ieee.org> > >For policy questions, send mail to: >Jim Bacher: <j.bac...@ieee.org> >David Heald: <dhe...@gmail.com> >_________________________________________________ >To unsubscribe from the EMC-PSTC list, click the following link: >https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1 - ---------------------------------------------------------------- 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://www.ieee-pses.org/emc-pstc.html 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: Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
