RE: Thermal effects on EMC and Earth Leakage
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 f...@netc.ie -Original Message- From: Peter Merguerian [mailto:pmerguer...@itl.co.il] Sent: 18 December 2001 14:47 To: 'duncan.ho...@snellwilcox.com'; emc-p...@majordomo.ieee.org 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: duncan.ho...@snellwilcox.com [mailto:duncan.ho...@snellwilcox.com] Sent: Monday, December 17, 2001 5:59 PM To: emc-p...@majordomo.ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived
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: duncan.ho...@snellwilcox.com [mailto:duncan.ho...@snellwilcox.com] Sent: Monday, December 17, 2001 5:59 PM To: emc-p...@majordomo.ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
Re: Thermal effects on EMC and Earth Leakage
How much of a temperature increase are we talking about, how much do emissions increase, and what frequency(s) increase in emissions? - Doug McKean --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
RE: Thermal effects on EMC and Earth Leakage
Have a look at the manufacturer's data sheets for the capacitors, and you'll see spec's or graphs indicating the % capacitance change vs. temperature. This can be substantial for ceramic cap's in particular. I don't know how much of an effect it is for the typical film-type X and Y cap's, but that is likely the source of the change in leakage current. Keep in mind that the EMC performance of a SMPS may be related to many factors, not just X or Y capacitor performance. There are often capacitors located further inside the product that are not X or Y types (and aren't required to be) yet serve an EMC-reduction function, that could be ceramic types with significant value change vs. temperature. There will also be temperature-related changes in electrolytic filter cap's, magnetic components, snubbers, the power semiconductors themselves, etc. Many of these changes may seem subtle in absolute value, but given the impact that parasitics have on EMC, the change could make a big difference. Jim Eichner, P.Eng. Manager, Engineering Services Xantrex Technology Inc. Mobile Power phone: (604) 422-2546 fax: (604) 420-1591 e-mail: jim.eich...@xantrex.com web: www.xantrex.com -Original Message- From: duncan.ho...@snellwilcox.com [mailto:duncan.ho...@snellwilcox.com] Sent: Monday, December 17, 2001 7:59 AM To: emc-p...@majordomo.ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
RE: Thermal effects on EMC and Earth Leakage
I can't speculate on the reason for the increase in leakage current; however, I suspect you have a thermal design problem with the switching circuit. I have seen an increase in conducted emissions due to a change of the switching waveform - e.g. rise and fall times and ringing - once the product has reached operating temperature. I have also seen this problem vary from unit to unit due to spurious switching noise on the waveform. Richard Woods Sensormatic Electronics Tyco International -Original Message- From: duncan.ho...@snellwilcox.com [mailto:duncan.ho...@snellwilcox.com] Sent: Monday, December 17, 2001 10:59 AM To: emc-p...@majordomo.ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson:pstc_ad...@garretson.org Dave Healddavehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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.
