In a messaged date 1/8/2004, Richard Hughes writes: > It is my belief that the dielectric withstand test is that required > for basic insulation for a PRIMARY circuit, not a SECONDARY circuit - > although I agree the requirement is not as clear as it could be. > If you look at Annex ZB it tells you to "add the following text > between the first and second paragraph", part of the text being "each of > which shall pass the electric strength test below" and the second para
> has the text "insulation shall have a minimum d.c. sparkover voltage of > 1,6 times the RATED VOLTAGE or 1,6 times the upper voltage of the RATED > VOLTAGE RANGE of the equipment" > ....The dielectric strength requirements have been increased by a > factor of 1.6x. Hi Richard: It appears that we are in agreement on most points except the one excerpted above. I think the problem is that the wording in Annex ZB is very poor and can be interpreted different ways. I interpret the Annex ZB reference to "the electric strength test below" to be pointing to the values listed in the main body text of clause 6.1.2.1, namely, a test voltage of 1500 VRMS for installations where the AC mains voltages exceeds 130 VRMS and a test voltage of 1000 VRMS elsewhere. I do not think that ordinary solid insulation has to be tested to 1.6 times 1500 VRMS. After laying out the requirement for ordinary solid insulation, Annex ZB goes on to describe three special cases where alternate requirements can be applied to the solid insulation: 1) A "semiconductor component" such as an opto isolator 2) A Y2 cap 3) A Y3 cap The reference to a test of 1.6 times 1500 VRMS is for the first of these special cases, "semiconductor components." Just to make things more confusing, the main body text in clause 6.1.2.1 uses the same factor of 1.6 in a different context. The statement that surge suppressors must have a minimum sparkover of 1.6 times the RATED VOLTAGE is referring to the nominal AC mains voltage, not the test voltage for electric strength. The RATED VOLTAGE is defined in clause 1.2.1.1 and would likely be about 250 VRMS for a product used in Finland, Norway, or Sweden that is powered from the AC mains. The other topic where we may not completely agree is the question of whether the applicable requirement is for a primary circuit or a secondary circuit. I would argue that for the purposes of clause 6.1.2.1 this question is now moot, since there is no longer any reference in clause 6.1.2.1 to a requirement where one first needs to determine whether the circuit is a primary circuit or a secondary circuit. The place where this distinction still needs to be considered is the basic insulation requirement in clause 2.3.2. In this case the barrier is between (SELV or TNV-1 or accessible parts) and (TNV-2 or TNV-3). A TNV circuit is considered to be a secondary circuit, so Table 2K applies instead of Table 2H. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Richard Hughes > Sent: Thursday, January 08, 2004 4:22 PM > To: [email protected] > Cc: 'Ron Pickard'; [email protected] > Subject: RE: EN60950-1,TNV to Earth Insulation > > > > Ron, > > > > Joe Randolph wrote: > > > Hi Ron: > > > > In my interpretation of EN 60950-1, the insulation > requirement is the > one contained in the main body of the > text, UNLESS it is modified in > Annex ZB. In that case, > the modifications called out in Annex ZB also > apply. > > REH> Pretty much, except more precisely the requirements of Annex ZB > replace any conflicting requirements in the body of the standard in > Finland, Norway and Sweden (in this particular case). > > > > > So, there has in fact been a relaxation of the traditional > Nordic > requirement for supplementary insulation. The > revised Annex ZB retains > only the solid insulation aspects > of supplementary insulation. The > creepage, clearance, and > electric strength requirements are now the ones > in the > main body of the document, namely, basic insulation for a > > secondary circuit. > > REH> It is my belief that the dielectric withstand test is > that required > for basic insulation for a PRIMARY circuit, not a SECONDARY circuit - > although I agree the requirement is not as clear as it could be. > REH> If you look at Annex ZB it tells you to "add the > following text > between the first and second paragraph", part of the text > being "each of > which shall pass the electric strength test below" and the > second para > has the text "insulation shall have a minimum d.c. sparkover > voltage of > 1,6 times the RATED VOLTAGE or 1,6 times the upper voltage of > the RATED > VOLTAGE RANGE of the equipment" > REH> That the requirement is for a PRIMARY circuit is also logical, > given the origional requirement for SUPLIMENTARY insulation for a > PRIMARY circuit and an understanding of the Nordic concerns. > > > > > > Note that while this might lead you to conclude that the > electric > strength requirement has been relaxed from the > 1500 VRMS of > supplementary insulation, the 1500 VRMS > requirement now appears in > clause 6.1.2.1 for cases where > the AC mains voltage exceeds 130 VRMS. > This change (an > increase from the previous requirement of 1000 VRMS) > took > place when the 3rd edition of EN 60950 was issued in the year > 2000. > That same edition was the first time the reference > to supplementary > insulation disappeared from Annex ZB. > > > You ask whether the solid insulation requirements in Annex > ZB apply to > printed wiring boards. In my interpretation > they certainly do. In > earlier versions of Annex ZB that > explicitly called out supplementary > insulation, there was > always the option of using the various printed > circuit > board construction methods that now appear in clause 2.10.5.3 > of > EN 60950-1 (these options have appeared in earlier > editions in different > clauses). Now that Annex ZB makes > no explicit reference to > supplementary insulation, some > people might argue that the options > described in clause > 2.10.5.3 can not be used. I think these options can > still > be used, but doing so might require some additional > justification > to show that the result complies with the "2 > thin layers" option in > Annex ZB. > > REH> Yes, the solid insulation requirements would apply to most pcbs > with the proviso's mentioned by Joe. > > > In summary, the net effect of the changes for Finland, Norway, and > > Sweden is that the creepage and clearance requirements have been > > relaxed, but the requirements for solid insulation and > electric strength > > remain the same as they were when the requirement called out > > supplementary insulation. > > REH> The dielectric strength requirements have been increased by a > factor of 1.6x. > > > > > By the way, I have formed the impression that the reason for the > > difference between the IEC version and the EU version is > that there have > > been ongoing efforts to get the Nordic countries to drop their > > insistence on supplementary insulation and harmonize their > requirement > > with the rest of the EU (and in fact, the rest of the countries > > worldwide that base their requirements on IEC 60950). I think the > > difference that we see is the result of a compromise that > was worked out > > between the time that the IEC version was completed and > the time that > > the EU version was published. > > > REH> True > > > > > > Joe Randolph > > Telecom Design Consultant > > Randolph Telecom, Inc. > > 781-721-2848 (USA) > > [email protected] > > http://www.randolph-telecom.com > > > > > > > -----Original Message----- > > > From: [email protected] > > > [mailto:[email protected]] On Behalf Of > Ron Pickard > > > Sent: Wednesday, January 07, 2004 4:38 PM > > > To: [email protected] > > > Cc: [email protected] > > > Subject: Re: EN60950-1,TNV to Earth Insulation > > > > > > > > > > > > > > > Hi Richard, > > > > > > Thanks for your detailed response. However, Annex ZB > > > (6.1.2.1) only pertains to insulation that is solid or forms > > > part of a semiconductor component, to Y2 capacitors and to Y3 > > > capacitors with conditions. Is the reference to solid > > > insulation meant to include printed wiring boards? If not, > > > then basic insulation for a secondary circuit is all that's > > > required now. So, basically (please excuse the pun), the only > > > missing part of the TNV-SELV insulation equation would be the > > > working voltage across the barrier. Is this a fair assessment? > > > > > > Best regards, > > > > > > Ron Pickard > > > [email protected] > > > > > > > > > > > > > > > > > > [email protected] > > > > > > > > > m To: > > > [email protected] > > > > > > cc: > > > [email protected] > > > > > > 01/07/2004 01:34 Subject: Re: > > > EN60950-1,TNV to Earth Insulation > > > > > > PM > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Ron, > > > > > > When you look at "in some countries" notes in IEC standards > > > you will see that they have all disappeared when it comes to > > > CENELEC standards (unless the publishing organisation hasn't > > > done its job correctly). The reason for this is because > > > European deviations are relocated to Annex ZB or Annex ZC and > > > all non-European deviations are just stripped out all together. > > > > > > Annex ZB contain what is known as "Special National > > > Conditions". As the term implies, they are applicable in > > > some countries only (i.e. not across the whole of Europe - > > > such things are called "Common > > > Modifications") and they result from characteristic > (e.g. the local > > > environment) or practice (commonly building wiring > > > regulations / national electric codes) that cannot be changed > > > even over a long period. Look here and this is where you > > > will find the deviations for Finland, Norway and Sweden that > > > relate to clause 6.1.2.1. > > > > > > > > > Annex ZC contain what is known as "A-deviations". Typically > > > these stem from national laws. You will see that there is a > > > Note that states that > > > "it is the view of the Commission of the European > > > Communities ... that compliance with A-deviations is no > > > longer mandatory and that the free movement of products > > > complying with such a standard should not be restricted > > > except under the safeguard procedure provided for in the > > > relevant Directive". Of course, if a company chooses to > > > ignore these deviations and is prosecuted for failure to > > > comply with some national law or other, the opinion of the > > > European Commission may be moot. > > > > > > But what of Annex ZA? That is just a list of standards that > > > have been Normatively referred to (they must be met, where > > > they are specifically called up) where the references to > > > international publications have been replaced by their > > > relevant European counterparts. > > > > > > Now to your specific question... > > > > > > Is supplementary insulation for a primary circuit still > > > required in order to comply with clause 6.1.2.1? > > > > > > Short Answer, NO. > > > > > > Detailed Answer, See Annex ZB (Page 252 if you have BS > EN 60950-1). > > > > > > Best regards, > > > > > > Richard Hughes > > > > > > Safety Answers Ltd > > > www.safetyanswers.ltd.uk > > > > > > > > > > > > > > > > > > Ron Pickard wrote: > > > > > > > > > > > To all those knowledgeable with the 60950 series of safety > > > standards, > > I've just been able to receive my copy of > > > EN60950-1 (I've had IEC > 60950-1 for some time now). Upon > > > > leafing thru EN60950-1, I noticed something missing that > > > was in notes > 1 & 2 of clause 6.1.2.1 of > IEC60950 3rd > > > Ed. That being, the requirement for supplementary > > > > insulation for a primary circuit for > Norway and Sweden > > > from TNV to earth. And looking into IEC60950-1, the > note > > > in clause 6.1.2.1 states > "In Finland, Norway and Sweden, > > > there are additional requirements for > the insulation." > > > > Unfortunately, I've looked in clauses 2.3, 2.9, 2.10 and 6.1, > > > but > cannot find these additional > requirements (even the > > > CB Bulletin appears to provide only solid > insulation > > > requirements for > 6.1.2.1). And to make this matter a bit > > > more obtuse, both notes in > clause 6.1.2.1 has been deleted > > > > from EN60950-1 according to Annex NA. > > So.... I have > > > to ask, is supplementary insulation for a primary > circuit > > > still required here? If so, > where is the requirement > > > actually stated? Or, is supplementary > insulation for a > > > secondary circuit, > or even basic insulation, now > > > acceptable for Norway and Sweden? > > Or, have I overlooked > > > something? I'm trying get thru the cobwebs back > to > > > daylight and I'm hoping > that you will help me and maybe > > > others with the same question(s). > > I look forward to > > > your replies. Please advise. > > Best regards, > > Ron > > > Pickard > [email protected] > > > > > > > > ------------------------------------------- > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------------------------------- > > > 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 > > > > > > > > > ------------------------------------------- > 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 > 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
