Hi Rich.
The exception being Table G.2 of IEC60950, 3rd ed. Table G.2 clearly states
its applicability up to 2km, when using Annex G and its Alternative method
for determining minimum clearances.
Peter L. Tarver, PE
ptar...@nortelnetworks.com
From: Rich Nute [mailto:ri...@sdd.hp.com]
Hi
If you trace down the location of the breakdown, I'll bet you'll find spacing
violations there.
There is a pretty good margin built into the dielectric strength tests. I often
go
well beyond the test limits on type tests just to find the weak spots and
assure a
margin for production tests.
Hi Doug:
IEC 60950 differs from IEC 60664 in that the clearances
are for sea level, not 2000 meters. See Table 18, Note
2.
Since 664 is the reference standard, I suppose one can
ask whether the 950 authors correctly transposed the
2000-meter clearances from 664 to sea level clearances
for
Hi John:
clause 5.3 allows for altitude correction, but the standards dont mention
any
correction factors with regard to clause 6.4.
Sub-clause 5.3 invokes electric strength testing.
Physics correctly predicts breakdown voltage for
a given clearance decreases with altitude. The
John,
According to IEC664 (and as a result, all derived standards), altitude
correction is normalized to 2000 meters (6562 feet) for a nominal barometric
pressure of 80 kPa. This calculation is based on Paschen's Law and covers
most of the populated areas of the world. This altitude correction
John,
I would ask your friendly UL engineer how they test this, especially in
Denver! Since UL/ANSI is a representative to the IEC 950 committee, they
might be interested whether this correction was inadvertently omitted from
Clause 6.4, or was intentionally left out! And yes, we'd all be
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