In message <[email protected]>,
dated Tue, 13 May 2014, "ce-test, qualified testing bv - Gert Gremmen"
<[email protected]> writes:
- Creepage breakdown is an essential long time process governed by
dissipation effects on a surface layer covering the creepage path. The
properties of that layer are ruled by pollution degree and material
group (CTI-value) and possible other factors left out in IEC 61010. As
dissipation is linear with working voltage RMS values, its RMS value
that need to be taken into account for calculating creepage values.
I don't think that dissipation necessarily causes, or even correlates
with, the growth of a conductive layer on an insulator. Electrochemical
processes are driven directly by voltage, not heat. Because of the
difficulty of predicting such effects, since they depend on the
particular environment, it is *prudent* to base creepage distance
requirements on peak voltage, especially as this often presents no
particular difficulty.
--
OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk
Nondum ex silvis sumus
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
-
----------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society emc-pstc discussion
list. To post a message to the list, send your e-mail to <[email protected]>
All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html
Attachments are not permitted but the IEEE PSES Online Communities site at
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used
formats), large files, etc.
Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html
For help, send mail to the list administrators:
Scott Douglas <[email protected]>
Mike Cantwell <[email protected]>
For policy questions, send mail to:
Jim Bacher: <[email protected]>
David Heald: <[email protected]>
