34 SYNCHRONOUS MOTORS 



magnitude and in phase to the vector of the current, it suffices, there- 

 fore, to attribute to it, as an axis of reference for phases, a right 

 line Y'A 2 Y, which makes, with OX, the axis of reference for the 

 E.M.F's., an angle equal to 7-, and having A 2 Y' for its positive direc- 

 tion. We thus obtain the diagram Fig. 22. 



This diagram is bipolar because the axis to which the E.M.F. E 2 is 

 referred is the horizontal line OX, and the vector E\ turns around O 



FIG. 22. 



as a center; whereas the current vector A ^A 2 turns around A 2 and is 

 referred to the axis YA 2 Y'. 



The diagram of Fig. 22 shows that the current is more or less directly 

 opposed to the E.M.F. E 2 . It can be decomposed into two compo- 

 nents, one directly opposed, the other having a phase-difference of . 



2 



This decomposition is easily made on the diagram (Fig. 23) by pro- 

 jecting the vector A 2 Ai on the line A 2 Y and on a line (A\D) perpen- 

 dicular thereto. We thus obtain: 



(i) The component having the same phase as E 2 which, following 

 the expression of Dolivo-Dobrowolsky, we will call the " watted " 

 current, 



I W = A 2 D. 



