I am not sure what you are trying to meet, spec-wise, but if I was trying to
pass VDE or TUV here in the states, My clearance chart indicates for 250V
RMS working voltage on the primary side of any power supply, between AC Hot
and AC Neutral you would need 3mm or .120 inches creep if not protected from
contaminants...
Between AC Hot or Neut and AC Ground you would need 4mm or .160 inches of
creep.
380 ACV-RMS working voltage would be .026 inches more added to the above
figures based on the .0002 in. per volt rule... I would guess. Of course the
place to present the question is with the agency you are trying to get
approval from. Most of the agencies will approve deviations from this guide
by demonstration in test. But that is an expensive process that most like to
avoid by design.... It's best to get numbers directly from the testing
agency.

As an added note, IPC-D-275 states from 301-500 V peak... below 10,000 ft.
altitude you need .1 inch creep.
above 10,000 ft you need .5 inches. This of course is for external layers,
uncoated, unprotected from contaminants...

Personally, we have passed Hi-pot at 4KV with a gap of .087 so it's really
up to the agency you are trying to pass what actual spacing you will need.
The guides are based on worst case studies and have margin built into them
to cover most all potential conditions...which may not necessarily be
applicable to Coffee Pots.

- Bill Brooks


-----Original Message-----
From: Radaelli Roberto [mailto:[log in to unmask]]
Sent: Wednesday, June 07, 2000 8:17 AM
To: [log in to unmask]
Subject: [TN] info about creepage distance


hi to all
i want to know the minimun distance between two trace on a standard fr4
material
with a pollution level of 2 (from vde0110).

the voltage is 230vac for the trace under the mains and 380vac for the power
section
in europe we look a table from CEI EN 60335-1 that say to use 1 mm every
100v for
level 2 of pollution and 1 mm every 150v for 2 level

is there similar for UL standard ?

we make coffee machine and i look on the UL197 standard (table 28.1) that
say a minimun
distance of 4mm or 3.2mm for 126 to 250vac (in the U.S. we sell only single
phase machine).


thank's a lot
roberto radaelli
rancilio coffee machine
e-mail [log in to unmask] <mailto:[log in to unmask]>

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