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-Original Message-
From: Peter Merguerian [mailto:pmerguer...@itl.co.il]
Sent: 18 December 2001 14:47
To: 'duncan.ho...@snellwilcox.com'; emc-p...@majordomo.ieee.org
Subject: RE: Thermal effects on EMC and Earth
Duncan,
I am not into physics, but I can give you a good direction. UL rates X and
Y-caps at 85 deg C max. There is a reason behind this and one way is ask a
UL capacitor expert. When you have find the information you need, please
share it with us.
This e-mail message may contain privileged
How much of a temperature increase are we talking about,
how much do emissions increase, and what frequency(s)
increase in emissions?
- Doug McKean
---
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion
Have a look at the manufacturer's data sheets for the capacitors, and you'll
see spec's or graphs indicating the % capacitance change vs. temperature.
This can be substantial for ceramic cap's in particular. I don't know how
much of an effect it is for the typical film-type X and Y cap's, but
I can't speculate on the reason for the increase in leakage current;
however, I suspect you have a thermal design problem with the switching
circuit. I have seen an increase in conducted emissions due to a change of
the switching waveform - e.g. rise and fall times and ringing - once the
product
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