180 



ALTERNATING CURRENTS 



These large leakage fluxes would cause the transformer regula- 

 tion to be too poor for commercial use. To reduce the leakngo, 

 the primary and secondary should be interleaved. Therefore, 

 each is usually split into a number of coils, and alternate primary 

 and secondary coils are placed together, as shown in Figs. 183 and 

 184, pages 196 and 197. 



80. Transformer Vector Diagram. Figure 174 (a) shows the 

 relations existing among the currents and voltages in a trans- 

 former, when the secondary is delivering a current 7 2 , at terminal 

 voltage F 2 and power-factor cos 62- A one-to-one ratio of trans- 

 formation is assumed, in order that the lengths of all the vectors 



'*' 



FIG. 174(6). 



FIG. 174 (a). Complete vector diagram Tor a transformer. 

 FIG. 174 (6). Energy and magnetizing components of no-load or exciting 

 current. 



in the diagram shall be of the same order of magnitude. This 

 same diagram may be made applicable to any ratio of trans- 

 formation, merely by multiplying the proper vectors by the ratio 

 of transformation. 



The secondary current 7 2 is laid off at phase angle 2 from the 

 secondary terminal voltage F 2 . The secondary leakage flux </> 2 

 is in time-phase with / 2 and induces the emf . which is balanced 

 by I 2 X 2 , leading 7 2 by 90. The induced voltage E z of the sec- 

 ondary is determined by adding vectorially to Vz the secondary 

 resistance drop 7 2 # 2 , in phase with 7 2 , and the secondary react- 



