182 ALTERNATING CURRENTS 



The primary terminal voltage F> may now be found by adding 

 IiRi and I\X\ vectorially to E\. 



The transformer regulation is defined as the rise in secondary 

 voltage divided by the rated-load voltage, when rated-load is 

 removed from the transformer. The primary voltage is assumed 

 to be constant. 



The regulation for a one-to-one transformer is given by 



Vi - V* 

 V 2 



81. Simplified Diagram. The diagram of Fig. 174 may be 

 materially simplified if the magnetizing current 7 be neglected. 

 As /o is usually from 3 to 8 per cent, of I\ and the two are con- 



'2 



FIG, 175. Transformer diagram with primary voltages rotated to secondary 



side of diagram. 



siderably out of phase, 7 may ordinarily be neglected without 

 serious error. Figure 175 shows the diagram of Fig. 174 with 7 

 omitted. Note that -Ei is 180 from # 2 ; /i is 180 from 7 2 ; 

 IiRi is 180 from 7 2 # 2 ; and IiX l is 180 from 7 2 X 2 . Therefore, 

 if the entire left-hand side of the diagram be rotated through 

 180 with the origin as a center, as shown in Fig. 175, EI 

 and E 2 coincide, I\R\ and I\X\ become parallel to I 2 R 2 and 7 2 Jf 2 

 respectively. 



As 7i equals 7 2 , the two IR drops may be combined into a 

 single drop equal to 7 2 (Ri + Rz) and the two IX drops may be 

 combined into a single drop equal to 7 2 (Xi + X 2 ), as shown in 

 Fig. 176 (a). Let Ri + R 2 = RO and Xi + X 2 = X . It is to 



