142 THE DESIGN OF STATIC TRANSFORMERS 



until the ultimate temperature is reached. This is the case 

 because the oil rises to the top after being heated by the trans- 

 former. T2, situated near the body of the transformer which 

 is the seat of the losses, presents a similar characteristic 

 although the value of the temperature is not so great. Trt. :it 

 the bottom of the case, presents a different shape of heating 



2 3 <? 5 (> '/ G <?> /O // / 



I'/rne //? Hours . 



FIG. 85. Temperature test on a 10-kva single-phase transformer, \villi a load of 

 8 kw. (For positions of thermometers T lf T 2 , T 8 , see Fijr. si.) 



curve. The temperature rises very slowly at first for a con- 

 siderable number of hours, and then more rapidly as the entire 

 transformer becomes heated up. 



This fact has been also pointed out by Epstein 1 and some of 

 his tests have already been shown in Fig. 76 (p. 119). It will be 

 observed that the lower the thermometer is placed in the oil 



1 "Testing of Electric Machinery and of Materials for its ( 'oust niH ion/' 

 Jour. I nst. Kluc. Kngrs., Vol. XXXVIII., p. I'.'. 



