Chris,
Only about your first question:
The values of temperature rises of table 16 are based on a temperature of 25
degrees, see sub-clause 1.4.7. A rubber handle can have a max. temperature
to touch of 25+50=75 degrees (not 85).
You will feel that the rubber is warm. If the handle is made of metal, you
may burn yourself at 75 degrees, that's why the temp rise of metal is
reduced to only 30 degrees (max temp of 55 degree).
If your product is specified for an environmental temp of 45 degrees, the
rubber handle may also not become hotter than 75 degrees, which means that
the temperature rise is only 30 (see also sc 1.4.7.
Regards,
Andre
From: "Chris Maxwell" <chris.maxw...@nettest.com>
Reply-To: "Chris Maxwell" <chris.maxw...@nettest.com>
To: "EMC-PSTC Internet Forum" <emc-p...@majordomo.ieee.org>
Subject: Safety: Temperature Rise and Capacitor Clearance (EN 60950)
Date: Wed, 30 Jan 2002 11:40:41 -0500
I have a couple of questions regarding this standard: (I have the 1992
version)
First
Table 16 specifies maximum temperature RISE for components, surfaces,...
What are the assumptions here? Are they assuming an ambient of room
temperature (25 deg C)? Which would mean that a rubber handle could
become as warm as 25 deg C + 50 deg C which is 85 deg C? This seems
high to me.
This would be even worse under high temperature ambients. For instance,
our products are typically specified to operate in ambients up to 45 deg
C. In this ambient temperature, Table 16 would appear to allow an
absolute temperature of 45 deg C + 50 deg C for an absolute temperature
of 95 deg C!!!!! This seems high to me. Any thoughts?
Second
I am planning on using high voltage hold-up capacitors in a high voltage
bus application (200VDC). The capacitors are aluminum electrolytic,
radial leaded, PCB mount with a safety vent. Nichicon The capacitors
will be the tallest components on a PCB within a metal chassis. The
metal cover going over them will be grounded. Do I need to leave a
clearance distance over the top of these capacitors for the safety vent
to operate? Do I need to leave a clearance between their top and the
grounded cover for dielectric withstand reasons? If the grounded cover
is within a few thousandths of an inch of the capacitor tops, do I need
to put some kind of mylar sheet in between insulate it from the
capacitors? (assuming that the cover could be bent to touch the
capacitors.)
Any advice would be welcomed and appreciated.
adTHANKSvance.
Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797
8024
NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 |
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