Grace, > One of our hardware design engineers comes up with a question for > rated voltage for a capacitor. > > Under the second page (Page 19) of the datasheet found at > http://www.avxcorp.com/docs/Catalogs/safecc.pdf, the rated voltage for > 61V is different when using as a X1 and when using as an Y1. The > question is: for a same capacitor, why is the rated voltage different > due to its usage (X1 400VAC vs Y1 250VAC)?
The short answer is "safety". Here is an excerpt from page 8-16 of my book, Robust Electronic Design Reference Book, Volume 1: "Capacitors that connect straight to primary power, such as ones used in AC-line filters, may be subjected to high-voltage spikes and surges, and thus require a surge-voltage rating. These capacitors are considered safety-critical parts by safety agencies, and usually must be certified to EN 60384-14, EN 132400, UL 1414, and CSA C22.2 No. 1. An X-capacitor goes line-to-neutral or line-to-line, and can not cause an electric shock if it fails. A Y capacitor goes line-to-ground or neutral-to-ground, and can cause an electric shock if it fails. These capacitors have several subcategories, with surge-test voltages of: · 4,000V peak for X1 capacitors. · 2,500V peak for X2 capacitors. · 8,000V peak for Y1 capacitors. · 5,000V peak for Y2 capacitors." John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, SM IEEE dBi Corporation http://www.dbicorporation.com/ - 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
