Rich, I can see your point. As a result of rapid polarity reversals, the acceleration of an ion across the mean free path of a gas will be halted and even reversed. I will read this paper to gain a better understanding but at this time I believe this will only affect gas breakdown as a result of impact ionization.
Thanks for the link, Doug On Tue, Aug 11, 2015 at 5:08 PM, Richard Nute <[email protected]> wrote: > > > > > Hi Doug: > > > > > > A simple (and therefore incomplete) explanation: > > > > Breakdown in air requires the ions to travel from one pole to the other > before the polarity reverses. At high frequencies, the polarity reverses > before the ions can travel the distance between the poles. > > > > At high frequencies (compared to mains frequencies) the clearance can be > less. See: > > > > http://lss.fnal.gov/archive/other/ssc/sscl-539.pdf > > > http://ewh.ieee.org/r10/taiwan/pses/archive/2012_04_27/IEEE%20PSES%20April/TC108%20hf_FC_v.1.2_IEEE%20PSES%20TAI.pdf > > > > > > > > Best regards, > > Rich > > > > > > ---------- Original Message ---------- > From: Doug Powell <[email protected]> > To: [email protected] > Subject: [PSES] IEC 61010-1 Table K.17 > Date: Fri, 7 Aug 2015 16:47:28 -0600 > > All, > > I am evaluating spacings for an RF product that operates at 13.56 MHz and > can produce maximum voltages of 5,000 Vrms (7,070 Vpk). If I do an > interpolation of using Table 6 (Mains 230 V, OV Cat II, indexing on 5,000 > Vrms), I get a minimum clearance requirement of 14.9 mm. When I do the > same calculation on Table K.17 (column 3, indexing on 7,070 Vpk), I get > 12.7 mm. > > Now I understand the effects of high frequency voltage stress causing air > molecules to become more energetic and therefore more likely to break down > at lower voltages. So why in this case does IEC 61010-1 Table K.17 result > in lower clearance values than Table 6? Somehow, this just seems wrong. > > *Please note that in the case of high frequencies paragraph K.3.1 > indicates I am to skip over section K.3.2 with the D1 + F × (D2 – D1) > calculations.* > > Thanks a bunch! > > Doug > > Douglas E Powell > [email protected] > http://www.linkedin.com/in/dougp01 > -- Douglas E Powell [email protected] Skype: doug.powell52 http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- 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]>
