s-c] 



CIRCLE DIAGRAM. 



189 



10 or n, may, for most practical purposes, be considered as 

 correct. This makes it possible to use the single equivalent 

 values for R and X obtained by the short-circuit test of Exp. 

 5-B, and does not require separate values 

 of R and X for the primary and sec- 

 ondary circuits. 



22. Again, the voltage which causes El 

 I to flow is Tip, as is seen in Fig. 6. In 

 the simplifications, this voltage is taken 

 as E 2 (Fig. 8) which is, say, i per cent, 

 less, or as E (Fig. 9) which is, say, 

 i per cent, more than the value of 

 Ep in the actual cases of Fig. 6. This 

 would make an insignificant change 

 in the value of 7 which is itself 

 small. In the latter case 7 depends 

 only upon line voltage and is independ- 

 ent of load. 



23. Diagrams Compared. Let 



us 



-- P- ---- O 



Flux 9) 



Simplified dia- 



compare the exact diagram, Fig. 7, with gram; R and X all in pri- 



, . ,.,, . T-,. mary. Corresponds to Fig. 8. 



the simplifications, Figs. 10 and n. 



In Fig. 7, the primary and secondary RI drops are in phase 

 with 7 X and 7 (2) , respectively, the XI drops being in quadrature. 

 The phase difference between 7 and 7 (2) is small much smaller 

 in fact than shown in the figure. The primary and secondary 

 drops may, accordingly, be combined with little error. This 

 may be done by taking the combined resistance drop in phase 

 with 7 t (Fig. 10), or in phase with 7 (2) (Fig. n). The com- 

 bined reactance drop is, in each case, at right angles to the 

 combined resistance drop. In an actual case little error is 

 introduced by these simplifications and either may be used, as 

 is most convenient. 



