298 ELECTRICAL ENGINEERING 



E! =E' +!& = !'+ I^n+jxJ ....... (280) 



/i = /o + !' ............... (281) 



(282) 



I' = -I 2 (283) 



E' = ^E 2 . (284) 



7*2 ' 



E 2 = E + 7 2?2 = E + 7 2 (r 2 + jz 2 ) ........ (285) 



5fc?c- vy f = J 2 z = / 2 (fl + jX), where Z = .B + jX is the load im- 

 pedance .............. (286) 



E = E (cos ^+j sin 6), where cos is the load power 

 factor ............. (287) 



These equations may be combined as follows: 



= J?' (go - J6o) (ri + jxO + /' 

 + ^f^+7 2 (r 2 +jo: 2 )i 



712 



= E' (g Q - jbo) (ri + jxi) + /' 



n z 

 E' (a n - i 



E' (flfo - J6o) (ri + jxi) + /' (n + j Xl ) (r, 



+ ^2) + j (X + x 2 )\. . (288) 



If the exciting current is neglected, the first term may be dropped 

 and equation 288 becomes 



E, = /' fn + j^ + (^J \ (R + r z ) + j (X+ %) jl. (289) 



The error introduced is of the order of one per cent. 



Fig. 274 represents the transformer as a circuit. If secondary 

 quantities are represented by the equivalent primary quantities 

 the circuit in Fig. 275 may be used to represent the transformer. 



