'-LOAD CURRENT, POWER FACTOR, ETC. 81 



will appear fairly conclusive that the large firm can go furth. r 

 in the direction of a liberal outlay for material, so long as a 

 reasonal'l. improvi-im-nt in ^utility is thereby attainable, than 

 u small firm. Of course, in many individual cases these 

 general characteristics of small and large firms are compl- 

 reversed, and in such cases the reverse conclusions would hold. 

 Some curves showing the approximate ratio of labour co- 

 active material c< opper and iron (and oil for oil-cooled 

 transformers), are shown in I-'i^. 18 for both natural air-cooled 

 and oil-cooled transformers of various capacities. The cost of 



ig materials is n>t included in the results frm 

 which these curves are jd-.tti-d. Hut it is important 

 con.^; cost of tli.' mat. rial in 11 t: uade 



up 



I. Core. 



II. c.'pper. 



III. In-ulatinu' inatn 



l\. Oil 



\ I. Accessories (su( i 





