The changes have forced many who simply matched test rises to rises in the standard and assumed they were OK to do the testing right. It is now much more obvious that you need to account for recommended product ambient. If you have a 25 degree max product ambient, say so.
Strictly speaking, a change from 27 degrees Celsius to 28 degrees Celsius is a change of one Kelvin. Kelvin is the measurement unit and is used without the degree mark. One degree Celsius is a thermal energy level, a point on the temperature scale, not a temperature difference and is equivalent to 274.15 Kelvin. Maintaining semantic correctness in the standard was not worth the effort. Bob Johnson ITE Safety From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, April 29, 2003 9:43 AM To: Rich Nute Cc: [email protected]; [email protected] Subject: Re: Surface Temperature Limits Ladies and Gentlemen Richard Huges commented that 60950-1 had changed to absolute temperatures rather than a delta above ambient. I checked in CSA60950-1 and this is indeed the case. Personally I preferred the delta measurement, as it was easier to measure in the lab. The implications on testing are that the heating test has to be done at the highest rated ambient temperature, e.g. if the equipment is rated to operate at +5 to +30 Deg C, the heating test has to be carried out at at an ambient of +30DegC. This now complicates the thermals testing somewhat, in that it now has to be done in an oven, instead of on the bench in the lab which is temperature controlled at around 23deg C. Is this assumption correct? A second question is does anyone know why the limits were changed from a delta K to absolute degreesC? Regards Doug Beckwith Rich Nute <[email protected]> To: [email protected] Sent by: cc: [email protected] owner-emc-pstc@majordom Subject: Re: Surface Temperature Limits o.ieee.org 04/25/03 12:47 PM Please respond to Rich Nute Hi Brian: > In EN61010-1 section 10 and EN60950 safety standards, there are surface > temperature limits specification for Normal Condition based on an Ambient > Temperature of 40ºC. Our company makes analytical instrumentation and a new No, this is not true for IEC 60950. The temperature limits in IEC 60950 are temperature RISE limits, not absolute limits. > product we are working on is functionally very susceptible to room temperatures. > So, the operational specification in our manual says it must be in a room no > warmer than 30ºC. If you use IEC 60950, you would place the equipment in a 30 C ambient, and then measure the temperatures of the parts in question, and then subtract the ambient to get the temperature rise. > Question is, is it proper to consider surface temperatures for safety based on > a 30ºC ambient which would give us 10º more range to work with? Someone told The operating ambient temperature range is a manufacturer's spec. The safety standard does not tell you what ambient temperature your equipment must operate in. > me you could do this but it doesn't seem right to me. You are relying on the > building's air conditioning as a level of protection. Then I was told that if > the AC broke down it would be considered a Fault and then the 105ºC limit would > be applied. No. Ambient temperature outside the manufacturer's spec is not a fault condition. The user's responsibility is to operate the product within the manufacturer's temperature spec just as it is the user's responsibility to connect the equipment to the correct supply voltage. If the AC broke down, what would be the ambient temperature? The temperature is indeterminant, so no meaningful measurements could be made, and, likewise, no meaningful temperature limits could be set. Best regards, 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
