The formula for calculating the temperature rise of a winding can be found in Annex E of IEC 60950 - and all the experts in TC 74 can't be wrong ?? (I also found the same formula in my 1985 issue of IEC 380.
Different temperature coefficents for copper have been quoted, and as far as I can determine, the reason for this is as follows: Definition of "temperature coefficent of resistance" is "the ratio of the increase of resistance per degree C rise of temperature to the resistance at 0 degrees C", and for a "standard annealed copper conductor", this is 1/234.5 = .004264. However, "the ratio of the increase of resistance per degree C rise of temperature to the resistance at 20 degrees C" is apparently .00393. Regards, John Crabb, Development Excellence (Product Safety) , NCR Financial Solutions Group Ltd., Discovery Centre, 3 Fulton Road, Dundee, Scotland, DD2 4SW E-Mail :[email protected] Tel: +44 (0)1382-592289 (direct ). Fax +44 (0)1382-622243. -----Original Message----- From: Robert Macy [mailto:[email protected]] Sent: 13 May 2002 14:54 To: Bill Ellingford; [email protected] Subject: Re: Constant for Change of Resistance formula. Bill, Thanks for the site. Went there and found the same formula and constant I use. For copper, Temp Coeff = 3.9 x 10-3 Then I clicked on table of coeff and there was a very long list of materials, but the temp coeff of copper there was 6.8 x 10-3 ???!!! Any ideas for this disparity? - Robert - Robert A. Macy, PE [email protected] 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 ------------------------------------------- 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] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
