RE: SMPS Derating reqs for Altitude range of 5000-10000ft
Thank you for all your answers related to my question. I' ve got good ideas for this area and I appreciate your time and kindness to do it. Best wishes and Happy New Year to all of you! Regards, Carmen Filimon Leitch Canada -Original Message- From: Alexandru Guidea [SMTP:gui...@cae.com] Sent: Tuesday, January 08, 2002 8:57 AM To: 'Carmen.Filimon'; 'EMC Forum' Subject: RE: SMPS Derating reqs for Altitude range of 5000-1ft Importance: Low As mentioned by some colleagues in this forum, some thermal effects due to altitude are caused by reduced air density, which decreases the heath dissipation through convection. The percentage of heath dissipation by convection depends of the construction of each power supply (I don't believe most of the manufacturers are able to provide a number there). For terrestrial application, the convection being the dominant path, anything above 50% can be a good guess. By determining the density of the air at a given altitude versus normal operating level it can be determined the impact on convection, and ultimately the derating of the PS. To be noted that: forced air, or natural convection cooling processes are not affected the same way; PS' working in uncontrolled environments at high altitude can be affected by low ambient temperatures. And as a final note, sometimes the experiment is the fastest, easiest way. Alexandru Guidea CAE Inc. Canada (my opinion and only mine) -Original Message- From: Carmen.Filimon [mailto:carmen.fili...@leitch.com] Sent: Friday, January 04, 2002 11:28 AM To: EMC Forum Subject: SMPS Derating reqs for Altitude range of 5000-1ft Hi All I'm trying to find out what the specified operational altitude range(s) is (are) for power supplies (particularly switching mode ones). Do any of you know what that spec may be, and particularly what is the rule for derating at altitude for thermal issues. Many manufacturers don't specify a maximum altitude but instead design in enough thermal overhead to accommodate any reasonable terrestrial location. According to GR-63-CORE the operating range without derating is 1800m above sea level. If derating is required above 1800m then the manufacturer must specify any additional requirements. Is it a safety derating factor so that customers at 5000-1ft don't smell smoke? Do we have any recommendations for derating the operational temperature / power consumption of power supplies as the operational altitude increases? Any information or ideas you have would be appreciated. Regards, Carmen Filimon Leitch Canada --- 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: SMPS Derating reqs for Altitude range of 5000-10000ft
Hi Chris, Andrew, Carmen: With regard to safety, both effects of altitude must be considered: 1) effect of air pressure on the electric strength of air (clearance), and 2) effect of lower density air on the temperature of solid insulation. (Creepage is a surface degradation phenomenon that is solely a function of working voltage, and is independent of altitude. But, creepage can never be less than the parallel clearance, so the creepage may also be affected for those situations where the minimum clearance is greater than the allowed creepage.) Best wishes for the New Year, Rich --- 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: SMPS Derating reqs for Altitude range of 5000-10000ft
I agree that creepage and clearance distances change. However, I'm not sure if you can answer that it is not a power issue. If the power supply depends on air for cooling; wouldn't the less dense air at higher altitudes be less effective at cooling the supply? A rough guess (admittedly thought up as I'm typing this message) would be that the cooling effectiveness of air would vary proportionally with air density. A furthur stretch of that reasoning would lead me to believe that the power ratings of forced air cooled supplies would also vary with air density. It may not vary with one to one correspondence due to the fact that there are other cooling mechanisms such as radiative cooling which can occur without air. As altidude goes up, air density goes down. Wouldn't cooling effectiveness also go down leading to a slightly lower power rating for air cooled supplies? Chris Maxwell | Design Engineer - Optical Division email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024 NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA web www.nettest.com | tel +1 315 797 4449 | -Original Message- From: Andrew Carson [SMTP:acar...@uk.xyratex.com] Sent: Friday, January 04, 2002 12:59 PM To: Carmen.Filimon Cc: EMC Forum Subject: Re: SMPS Derating reqs for Altitude range of 5000-1ft Carmen If your power supply is approved to IEC60950, then normally it will be approved upto 2000m. Above this altitude the required creepage and clearance distances start to increase. It is an electrical insulation issue, not a thermal issue. Carmen.Filimon wrote: Hi All I'm trying to find out what the specified operational altitude range(s) is (are) for power supplies (particularly switching mode ones). Do any of you know what that spec may be, and particularly what is the rule for derating at altitude for thermal issues. Many manufacturers don't specify a maximum altitude but instead design in enough thermal overhead to accommodate any reasonable terrestrial location. According to GR-63-CORE the operating range without derating is 1800m above sea level. If derating is required above 1800m then the manufacturer must specify any additional requirements. Is it a safety derating factor so that customers at 5000-1ft don't smell smoke? Do we have any recommendations for derating the operational temperature / power consumption of power supplies as the operational altitude increases? Any information or ideas you have would be appreciated. Regards, Carmen Filimon Leitch Canada --- 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. -- Andrew Carson - Senior Compliance Engineer, Xyratex, UK Phone: +44 (0)23 9249 6855 Fax: +44 (0)23 9249 6014 --- 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
Re: SMPS Derating reqs for Altitude range of 5000-10000ft
Actually, it is both. The decreasing density of air results in a lower voltage withstand and a lower rate of convection cooling.. IEC 60950 only addresses the safety aspect of the change, not the operational aspects. acar...@uk.xyratex.com (Andrew Carson)@majordomo.ieee.org on 01/04/2002 11:59:15 AM Please respond to acar...@uk.xyratex.com (Andrew Carson) Sent by: owner-emc-p...@majordomo.ieee.org To: Carmen.Filimon carmen.fili...@leitch.com cc: EMC Forum emc-p...@ieee.org Subject: Re: SMPS Derating reqs for Altitude range of 5000-1ft Carmen If your power supply is approved to IEC60950, then normally it will be approved upto 2000m. Above this altitude the required creepage and clearance distances start to increase. It is an electrical insulation issue, not a thermal issue. Carmen.Filimon wrote: Hi All I'm trying to find out what the specified operational altitude range(s) is (are) for power supplies (particularly switching mode ones). Do any of you know what that spec may be, and particularly what is the rule for derating at altitude for thermal issues. Many manufacturers don't specify a maximum altitude but instead design in enough thermal overhead to accommodate any reasonable terrestrial location. According to GR-63-CORE the operating range without derating is 1800m above sea level. If derating is required above 1800m then the manufacturer must specify any additional requirements. Is it a safety derating factor so that customers at 5000-1ft don't smell smoke? Do we have any recommendations for derating the operational temperature / power consumption of power supplies as the operational altitude increases? Any information or ideas you have would be appreciated. Regards, Carmen Filimon Leitch Canada --- 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. -- Andrew Carson - Senior Compliance Engineer, Xyratex, UK Phone: +44 (0)23 9249 6855 Fax: +44 (0)23 9249 6014 --- 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: SMPS Derating reqs for Altitude range of 5000-10000ft
From the Paschen curve, the electrical spacings must be increased 14% at 3000 meters over those at 2000 meters. Thermal derating is a tougher call since some smps vendors engineer in more cooling capacity than others. Testing for your application is the only reliable way to make a good determination if the manufacturer does not specify a derating curve. Daniel E. Teninty, P.E. Managing Partner DTEC Associates LLC Streamlining The Compliance Process Advancing New Products To Market http://www.dtec-associates.com (509) 443-0215 (509) 443-0181 fax -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Carmen.Filimon Sent: Friday, January 04, 2002 8:28 AM To: EMC Forum Subject: SMPS Derating reqs for Altitude range of 5000-1ft Hi All I'm trying to find out what the specified operational altitude range(s) is (are) for power supplies (particularly switching mode ones). Do any of you know what that spec may be, and particularly what is the rule for derating at altitude for thermal issues. Many manufacturers don't specify a maximum altitude but instead design in enough thermal overhead to accommodate any reasonable terrestrial location. According to GR-63-CORE the operating range without derating is 1800m above sea level. If derating is required above 1800m then the manufacturer must specify any additional requirements. Is it a safety derating factor so that customers at 5000-1ft don't smell smoke? Do we have any recommendations for derating the operational temperature / power consumption of power supplies as the operational altitude increases? Any information or ideas you have would be appreciated. Regards, Carmen Filimon Leitch Canada --- 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: SMPS Derating reqs for Altitude range of 5000-10000ft
Carmen If your power supply is approved to IEC60950, then normally it will be approved upto 2000m. Above this altitude the required creepage and clearance distances start to increase. It is an electrical insulation issue, not a thermal issue. Carmen.Filimon wrote: Hi All I'm trying to find out what the specified operational altitude range(s) is (are) for power supplies (particularly switching mode ones). Do any of you know what that spec may be, and particularly what is the rule for derating at altitude for thermal issues. Many manufacturers don't specify a maximum altitude but instead design in enough thermal overhead to accommodate any reasonable terrestrial location. According to GR-63-CORE the operating range without derating is 1800m above sea level. If derating is required above 1800m then the manufacturer must specify any additional requirements. Is it a safety derating factor so that customers at 5000-1ft don't smell smoke? Do we have any recommendations for derating the operational temperature / power consumption of power supplies as the operational altitude increases? Any information or ideas you have would be appreciated. Regards, Carmen Filimon Leitch Canada --- 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. -- Andrew Carson - Senior Compliance Engineer, Xyratex, UK Phone: +44 (0)23 9249 6855 Fax: +44 (0)23 9249 6014 --- 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.
