118 THE DESIGN OF STATIC TRANSFORMERS 



to rise for well on toward twenty-four hours. In Vol. 88 of 

 the Journal of the Institution of Electrical Engineers, Prof. 

 Kpstein publishes the curves of temperature rise reproduced 

 in Figs. 74 and 76, and relating to transformers manufactured 

 by the Felton-Guillaume-Lahmeyer Company. The curves 



FIG. 75. 40 000-volt oil-immersed transformer. 



in Fig. 74 relate to a 7,5-kw transformer, and it will be seen 

 that even at the end of sixteen hours the curves of temperature 

 rise of the core and the windings have only just become flat. 

 The curves of Fig. 76 relate to the temperature rise of the 

 40 000-volt oil-immersed transformer illustrated . in Fig. 75. 

 Prof. Epstein stated that he had found that " in all his firm's 

 transformers of the same design, from 3 up to 100 kw, the 



