http://www.ieee-pses.org/symposium
http://www.emc2004.org/
In my last email, I committed to providing an anecdote,
which follows below.
I first wish to make a few points:
1) I was not involved in the original product safety
evaluations;
2) my involvement with the product did not begin until just
before the below circumstance arose;
3) this e-mail specifically requests not haranguing or
proselytizing on the particulars of the product's
construction (the issue involves a hot button topic for some
posters to this group);
4) I'd prefer to limit the discussion, for now, to
compliance/conformance and the relationship of OSM Decisions
in that context;
5) I would appreciate a discussion of the consequences and
relevance of the safety certifications/licenses and test
reports, as they were issued, and where the "system" broke
down;
6) the below described issues have been thoroughly resolved
and no advice is needed to meet that end.
Product:
a network file server, Pluggable Equipment Type A, Class I
Equipment
European Safety:
CB Scheme Certificate and Test Report against IEC
60950:1999, issued APR2003, with one Amendment issued in
JUN2003, adding an alternate power supply; a MDoC against
the relevant directives and applied standards; a GS License,
issued by a well known, long established test house of
German parentage, who also issued the CB Certificate.
The alternate power supply has a CB Scheme Certificate and
Test Report against IEC 60950:1999, issued APR2003, and a
Bauart License, both issued by another, but different well
known test houses of German parentage.
Please keep in mind the parentage of the test houses and the
licenses granted as you continue reading.
How OSM Decisions came to be considered:
The server, containing the alternate power supply, was
deployed in Germany. As required by national law, the
product underwent testing in situ to determine continuing
compliance, but failed to comply with an insulation
resistance test specified in VDE 0702.
Imagine the confounding of the manufacturer, who in good
faith, attempted to comply with what they were advised were
the relevant and essential requirements for placing their
product in the market in the EU.
I was asked to investigate the issue and aid in resolution
of the "noncompliance."
Review of the power supply's construction showed use of MOVs
connected between phase and earth, and between neutral and
earth. Through additional testing, these MOVs were
determined solely responsible for the failure to meet the in
situ insulation resistance test. (As a side note, the power
supply contains a screw that provides the earthing contact
for the MOVs; loosening the screw allows compliance with any
required production line or type test EST.)
Review of the CB Scheme reports for the alternate power
supply and end-product shows no consideration given to the
use of MOVs in any of the documented National or Group
Differences. The MOVs are documented in the table of safety
critical components.
Review of IEC 60950:1999 shows no requirements or
particulars that prohibit the use of MOVs in the ac mains
supply connected between phase and earth, and between
neutral and earth.
Review of EN 60950:2000, in particular the documented
National or Group Differences, shows no requirements or
particulars that prohibit the use of MOVs in the ac mains
supply connected between phase and earth, and between
neutral and earth.
Review of the OSM Decisions clearly indicate a prohibition
of MOVs in the ac mains supply connected between phase and
earth, and between neutral and earth, but only in Austria,
Belgium, Denmark, Finland, Germany, Norway, Sweden and
United Kingdom; a *group* of countries, rather than being
panEU, that have established a *difference* in how to apply
Subclause 1.5.1 of EN60950:2000.
There you have it. You may dice it coarsely of finely, but
the above represents a *National or Group Difference* and
should be properly documented in both the EN version of any
and all effected standards and in the CB Bulletin. Simply
because factions within the EU chose to refer to this rose
by another name and claim it's existence is the result of
another process (ie, through CENELEC and its membership),
does not change the ultimate effect and amounts to
rationalization.
Regards,
Peter L. Tarver, PE
[email protected]
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