In most cases, Norway, Sweden and Finland? require supplementary insulation
for a primary circuit between TNV and Ground\/SELV. Assuming a primary
circuit of 250VAC, I believe this works out to 2.5mm creepage and 2.0mm for
clearance (I don't have my standard handy). In addition, you need 0.4mm
thickness through the board, or sufficient multi layers per 2.9.4.
Diaco, you didn't mention whether or not the product is intended for world
wide distribution, so be careful not to disregard these additional
requirements for these regions. I've heard that Sweden is considering a
compromise that might remove the distance through insulation requirement,
but still hold the line creepage and clearance, however, I don't know if and
when this will take effect.
Glenn
-----Original Message-----
From: Rich Nute [SMTP:[email protected]]
Sent: Thursday, October 08, 1998 8:54 PM
To: [email protected]
Cc: [email protected]
Subject: Re: Crepage/Clearance On Telecom Modem design
Hello Diaco:
My reading of Clause 6 of IEC 950/EN 60950 is:
between TNV circuit and primary circuit:
double or reinforced insulation, including applicable
creepage distance and clearance, or
basic insulation and a grounded conductive barrier,
including applicable creepage distance and clearance
from the primary circuit to the conductive barrier.
between TNV circuit and hazardous voltage secondary circuit:
double or reinforced insulation, including applicable
creepage distance and clearance, or
basic insulation and a grounded conductive barrier,
including applicable creepage distance and clearance
from the hazardous voltage circuit to the conductive
barrier.
between TNV circuit and SELV circuit:
no creepage distance or clearance requirement
(but, it must pass the hi-pot test)
between TNV circuit and ground:
no creepage distance or clearance requirement
(but, it must pass the hi-pot test)
Creepage distances are measured along the shortest path between
the two conductors across the surface of the insulator. There
is no correspondence to traces on opposite sides of printed
wiring boards (because such insulation is interposed solid
insulation, and MAY be subject to insulation thickness
requirements).
Best regards,
Rich
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