Richard,
>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"
The "1.6 x RATED VOLTAGE" requirement goes back to at least IEC950:1991
(6.3.3.1) where basic
insulation was required and I presume for a secondary circuit as it doesn't
specifically state that.
The primary circuit requirement came from Annex ZB (6.2.1.2), which was
specifically stated,
therefore leading one to believe that it would a secondary circuit normally.
Unfortunately, it is
not stated in EN60950-1 one way or the other, so I believe that it will be
left to interpretation
(and many a heated argument, I suspect). Actually, if a primary circuit is
applied, then this change
in the standard is all a matter of semantics (a rose by any other name is
still a rose). So,
treating it as a primary circuit, technically nothing changes from earlier
standards (its just
described differently). But, if its treated as a secondary circuit, creepages
and clearances will
likely be reduced.
But, is it for a secondary circuit or a primary circuit? That is the question.
I would say that its
a secondary circuit, but that's only my opinion, or interpretation.
>REH> The dielectric strength requirements have been increased by a
>factor of 1.6x.
Yes, according to Annex ZB (6.1.2.1), this 1.6x (2400Vac or 3394Vdc)
dielectric test applies only to
solid insulation of semiconductor components. Thinking about it, this new 1.6x
dielectric test
requirement may force some semiconductor bridging component sourcing changes
for manufacturers.
OK, its clear (well, sort of). Basic insulation is now required, but with
supplementary insulation
features (basimentary insulation, if you will :->), given Annex ZB (6.1.2.1)
of EN60950-1.
Comments?
Best regards,
Ron Pickard
rpick...@hypercom.com
richhug...@aol.co
m To:
j...@randolph-telecom.com
cc:
rpick...@hypercom.com, emc-p...@majordomo.ieee.org
01/08/2004 02:21 Subject: RE: EN60950-1,TNV to
Earth Insulation
PM
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)
> j...@randolph-telecom.com
> http://www.randolph-telecom.com
>
>
> > -----Original Message-----
> > From: owner-emc-p...@majordomo.ieee.org
> > [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Ron Pickard
> > Sent: Wednesday, January 07, 2004 4:38 PM
> > To: richhug...@aol.com
> > Cc: emc-p...@majordomo.ieee.org
> > 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
> > rpick...@hypercom.com
> >
> >
> >
> >
> >
> > richhug...@aol.co
> >
> >
> > m To:
> > rpick...@hypercom.com
> >
> > cc:
> > emc-p...@majordomo.ieee.org
> >
> > 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 > rpick...@hypercom.com > > > > >
> > -------------------------------------------
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