io6 



ELEMENTS OF ELECTRICAL ENGINEERING. 



desirable to consider the current (and voltage) in each winding as 

 positive when it flows in a given direction around the mesh, and the 

 arrows in Fig. 100 show these positive directions. On the basis 

 of this choice of signs, the clock diagram of the currents and 

 electromotive forces in the respective armature windings becomes 



main 3 



Fig. 100. 



symmetrical. The diagram of Fig. 99 represents the electro- 

 motive forces and currents in the armature windings, whether the 

 windings be Y-connected or A-connected. 



54. Manner of connecting receiving circuits to the three-wire 

 mains of a three-phase system. 



(a) For dissimilar receiving circuits (unbalanced system). In 

 this case the four-wire system should be employed as shown in 

 Fig. 94. This requires of course four collector rings on the 

 generator. A polyphase generator is, however, used primarily 

 for supplying currents to rotary converters and induction motors, 

 such machines always involve similar receiving circuits, one 

 receiving circuit for each phase, and when current is delivered 

 from a polyphase system to individual (single-phase) receiving 

 circuits, such as lamps, it is generally possible to distribute these 

 individual receiving circuits among the several phases so as to 



