Hi Doug:
I assume you are assuming the initiating event is an air breakdown as opposed to a solid insulation breakdown. Note that, according to Paschen's Law, air does not break down below about 323 volts peak (at sea level). The mains voltage does not exceed 170 volts peak (for 120 volts r.m.s.). So, when the initiating event is over, and the mains voltage goes through zero, the arc is extinguished and cannot start again. For two-wire equipment, the current depends on the two capacitances to ground. The first capacitor (transformer primary-to-secondary) breaks down, and the second capacitor (secondary circuit to ground) controls the current. Safety standards specify minimum clearances so that breakdown due to transient overvoltages is not likely. Hope this helps. Best regards and happy holidays, Rich -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Saturday, December 06, 2014 10:01 AM To: [email protected] Subject: [PSES] dielectric breakdown Hi Everyone, Is it possible that a fast breakdown of the dielectric barrier, by a fast event, like ESD or EFT, in a two wire mains power supply, cause a larger follow-on current from the AC mains and therefore a safety problem. How about follow-on current from a simultaneous lightning surge that would not by itself cause a breakdown? Anyone know of an incident of either type? I could set up an experiment but don't want to set my lab bench on fire. -:) Doug - ---------------------------------------------------------------- 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]>
