On 10/19/2006, Gary McInturff wrote:
The actual problem I’m having is that the line to ground capacitors on the pcb are blowing up at the figures the test house gave me and which are significantly higher than what I indicate above. Unfortunately they also arc during the surge testing at 2Kv and die there as well. Hi Gary: You did not provide all the necessary details for me to determine the relevant requirements, but if the input voltage is 120/240 VRMS AC mains voltage, the most commonly used type of capacitor would be a "Y1" safety rated cap. This type of capacitor is very robust and can typically withstand 4000 VRMS for one minute and an 8 KV impulse. So, if you are seeing capacitor failures, either you don't have Y1 caps or you have a manufacturing problem. The most common (and inexpensive) type of Y1 cap is a radial leaded ceramic disc. However, surface mount Y1 caps are also available, and these require careful attention during manufacturing. I have seen such caps develop microscopic cracks due to thermal stress if they pass through a wave solder process, or if they are in a location on the board that is subject to flexing. So, if the caps involved are surface mount and their specifications indicate that they should handle the test voltages, you may want to look closely for a possible manufacturing problem. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com <http://www.randolph-telecom.com/> ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
