72 THE DESIGN OF STATIC TRANSFORMERS 



wliicb, of course, is substantially independent of the load. Tin- 

 third column contains the copper loss, the fourth the total 

 input to the transformer, this being equal to the sum of the 



/00\ 



on Ts&nafor/ner 



FIG. 40. Curve showing variation of power factor with the load for a 

 20-kw transformer. 



three previous columns. The " power" efficienc}', i.e., the 

 ratio of column 2 to column 5 is given in column 6. 



TABLE 9. EFFICIENCY DATA OF 20-Kw TRANSFORMER. 



These values of the efficiency are plotted in Fig. 41, where 



