The temperature rating of the caps may be for different reasons. Firstly electrolytic caps can leak the electrolyte if operated at too high temperatures.
Secondly the MTBF of an electrolytic capacitor is related to the operating temperature. John Fee National Electronics Technology Centre Enterprise Ireland Phone +353-1-8082214 Fax +353-1-8370705 email [email protected] -----Original Message----- From: Peter Merguerian [mailto:[email protected]] Sent: 18 December 2001 14:47 To: '[email protected]'; [email protected] Subject: RE: Thermal effects on EMC and Earth Leakage Duncan, I am not into physics, but I can give you a good direction. UL rates X and Y-caps at 85 deg C max. There is a reason behind this and one way is ask a UL capacitor expert. When you have find the information you need, please share it with us. This e-mail message may contain privileged or confidential information. If you are not the intended recipient, you may not disclose, use, disseminate, distribute, copy or rely upon this message or attachment in any way. If you received this e-mail message in error, please return by forwarding the message and its attachments to the sender. PETER S. MERGUERIAN Technical Director I.T.L. (Product Testing) Ltd. 26 Hacharoshet St., POB 211 Or Yehuda 60251, Israel Tel: + 972-(0)3-5339022 Fax: + 972-(0)3-5339019 Mobile: + 972-(0)54-838175 -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Monday, December 17, 2001 5:59 PM To: [email protected] Subject: Thermal effects on EMC and Earth Leakage Group. I am interested to find out peoples opinions on a particular trend we've seen time and time again on most switch mode PSU's. It seems that once a PSU is warm its earth leakage decreases and its EMC emission performance decreases (i.e. it gets noisier). This would suggest that there is some sort of thermal effect, probabaly in the Y caps, that reduces their capacitance. Has anyone done any work in this area or can anyone explain the physics of this change. Is it as simple as expansion of the dielectric or is it more complicated than this? Any thoughts or opinions would be greatly recieved. Many thanks in advance, Duncan Hobbs ---------------------------------------------------------------------- The contents of this communication are confidential to the normal user of the email address to which it was sent. If you have received this email in error, any use, dissemination, forwarding, printing or copying of this email is strictly prohibited. If this is the case, please notify the sender and delete this message. ---------------------------------------------------------------------- ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
