148 



SYNCHRONOUS MOTORS 



vector 2' also represents (on the space phase diagram with right- 

 handed l armature rotation) the direction of the axis of an armature 

 coil when the induced E.M.F. is a maximum, just as the vector 7 

 represents both the time phase of the armature current and the direc- 

 tion of the axis of an armature coil when its current is a maximum, 

 which is thus the direction or space phase of the armature M.M.F. A. 

 The vector Ei drawn equal to Ez and in opposite phase, represents 

 that part of the impressed E.M.F. E\ necessary to balance the induced 

 E.M.F. (-2')- The impressed E.M.F. (E\) must then be equal to 

 Ei plus the E.M.F. Ir, in phase with /, consumed by the armature 



FIG. 72. 



resistance, and the E.M.F. Ix, 90 ahead of 7, consumed by the 

 leakage reactance of the armature. 



The diagram of Fig. 72 gives a fairly complete representation of 

 the relations involved in the operation of the synchronous motor. 

 Two assumptions are involved, however, which should be kept in 

 mind in case of a quantitative analysis: first, it is assumed that the 

 flux 4> is in the same direction as the resultant M.M.F. R; but in the 



1 It will be observed that the right-handed or clockwise armature rotation 

 here assumed for the space phase interpretation of the diagram corresponds to 

 the customary left-handed vector rotation in the time phase diagram. In the 

 case of a revolving field type of machine, the field must revolve left-handedly, 

 in order to give the same relative motion between armature and field. 



