1 86 



TRANSFORMERS. 



[Exp. 



a non-inductive branch for the in-phase component, /H, and an 

 inductive branch (without resistance) for the wattless quadra- 

 ture component /M. The currents which would flow in such 

 equivalent shunt circuits correspond exactly to the currents 

 / , /H and /M which actually flow in a transformer. 



'(2) 



E E 



Load 



mm 



FIG. 5. Complete equivalent of a transformer. The exciting current 7 

 is considered as flowing in a shunt circuit. The resistance and leakage react- 

 ance of primary and secondary are considered as external. Corresponds to 

 Fig. 3- 



19. The transformer proper, in Fig. 5, is considered as ideal, 

 all the losses being treated as external; / (2) = I 2 (S 2 -r-S 1 ) ; 

 and E P = E S (S^^-S 2 ). The voltage at the primary terminals, 

 E lt is more than EP on account of the drop in X^ and in R t . 

 Likewise, the voltage at the secondary terminals, E 2 , is less than 

 ES on account of the drop in X 2 and in R 2 . 



Load 



MM 



FIG. 6. Equivalent circuits as level (i : i) transformer. Corresponds to Fig. 7. 



The total primary current 7 X is seen to be equal to the load 

 current 7 (2) , plus (vectorially) the small no-load current / . 



20. Equivalent Circuits. The circuits of a transformer may 

 be represented more simply by the equivalent circuits of Fig. 6, 



