48 RATING OF ELECTRICAL MACHINERY 



GERMANY. The temperature limits specified for the rated load must 

 not be exceeded, therefore the overload must be applied for a sufficiently 

 short period and at a time when the temperature of the machine is 

 sufficiently low in order to insure that the permissible limits of temperature 

 cannot be exceeded. 



GREAT BRITAIN. Under no conditions must the temperature exceed 

 85 deg. cent. 



DBN. 



UNITED STATES. When the overload test is applied directly after the 

 rated load test under continuous service conditions, an allowance is per- 

 mitted of 15 deg. cent, above the limits specified for the rated loa<l. 



Surrounding Air Temperature Corrections 



BELGIUM. If the surrounding air is likely to exceed 35 deg. cent., the 

 temperature limits must be reduced by an amount equivalent to the excess. 

 FRANCE. If the test is carried out with a surrounding temperature 

 below 35 deg. cent., the temperature limits shall be reduced in the fol- 

 lowing ratio: 



1 



1 + 0.005 (35-0) . 



being the temperature of the surrounding air during the t< 



If the machine is intended for a locality in which the surrounding' air 

 exceeds 35 deg. cent., the temperature limits shall be reduced in the 

 following ratio: 



1 



1 +0.005 (0'-35) 



f)' being the presumed temperature of the surrounding 



Association Alsacienne. If the temperature of the surrounding air 

 ordinarily exceeds 35 deg. cent., the temperature limits must be reduced 

 by an equivalent amount. 



GERMANY. 



GREAT BRITAIN. If the surrounding air in actual service is likely to 

 exceed 25 deg. cent., the observed temperature rise shall be reduced 

 by one degree for each degree of difference between the surrounding air and 

 25 deg. cent. 



Swti 



UNITED STATES. The observed temperature shall be reduced or 

 increased one-half per cent for every degree cent, difference between the 

 surrounding air and 25 deg. cent. 



RESISTIVITY OF COPPER 

 Variation with Temperature 



Unless otherwise specified, the following values have been adopted: 



BELGIUM. 0.004 per degree cent. 



FRANCE. 0.004 per degree cent. 



GERMANY. 0.0040 per degree cent. 



(IREAT BRITAIN. 0.42 per cent per degree cent, from and at deg. cent. 

 \ EDEN. 0.004 per degree cent. 



UNITED STATES. 0.428 per cent per degree cent, from and at deg. 

 cent, for annealed copper of 100 per cent standard conductivity (see 

 Appendix E). 



ATMOSPHERIC PRESSURE 



UNITED STATES. 760 mm. of mercury. 



The observed temperature rise shall be reduced by 1 per cent for every 

 10 mm. deviation below 760. This correction is only to be applied when 

 the atmospheric pressure differs greatly from the standard pressure of 

 760 mm. of mercury. 



