If Gert means 'charge' in the number of Coulombs flowing, then the RMS value holds. If he means the charge 'capacity' attained then it is generally the peak voltage that holds.
A very loose analogy would be charging a capacitor with a varying voltage. The capacitor will charge to approaching the peak value, not the lower RMS value. T ----- Original Message ----- From: John Woodgate Sent: 05/13/14 09:23 AM To: [email protected] Subject: Re: [PSES] Creepage and RMS In message <[email protected]>, dated Tue, 13 May 2014, "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> writes: >Electrochemical reactions behave like charging a battery, it is the rms >value that determines the charge, not the peak value. I don not agree. I looked for a simple explanation on the web, but so far I found only quite complicated explanations based on the Nernst equation. However, I think you may see that the transfer of electrons from one substance to another, driven by an externally-applied electric field and creating conductive species, includes neither a squaring process or an averaging process. It's simply the reaction of the charged electrons to the field, and the field strength depends on the instantaneous voltage, not the RMS. However, I did explain that using the peak voltage is a *prudent* assumption. If it proves costly, a lower creepage distance should be tested, but it's difficult and costl! y to test anything that depends on pollution. Again, you can be *prudent* and test with a worst-case pollutant, soot or carbon from motor brushes. -- 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]> - ---------------------------------------------------------------- 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]>
