BIPOLAR DIAGRAM 



153 



irrent also enters. E.g., in Fig. 75 the armature current in every 

 )il reaches its maximum value when the axis of the coil has the 

 rection of the vector A or /; i.e., when the plane of the coil is in 

 ic line Ob, which differs from the direction of the flux $ by the 

 igle <]/. Thus the torque-producing effect of the current is reduced 

 from its maximum possible value, in the ratio cos <{/, and the torque is 



FIG. 75- 

 where k? is the constant of proportionality. But 



10 (R' 



where (R is the reluctance of the magnetic circuit and may for the 

 present be assumed constant. 



Then the output (which is proportional to the torque at constant 

 speed) may be written 



(i) 



