POLYPHASE CURRENTS.

97

from the generator, inserting in one motor circuit a dead resist-ance and in the other a self-induction coil, by which means adifference in phase between the two divisions of the current issecured. If both motors have the same number of field poles,the torque motor for a given number of alternations will tend torun at double the speed of the other, for, assuming the connec-tions to be such as to give the best results, its poles are dividedinto two series and the number of poles is virtually reduced one-lialf, which being acted upon by the same number of alternationstend to rotate the armature at twice the speed. By this meansthe main armature is more easily brought to or above the requiredspeed. When the speed necessary for synchronism is impartedto the main motor, the current is shifted from the torque motorinto the other.

A convenient arrangement for carrying out this invention is

Fig. 79.

Fig. 78.

shown in Fig. 80, in which .r .i are the field coils of the syn-chronizing, and h i the field coils of the torque motor, n l' arethe conductors of the main line. One end of, say, coils h is con-nected to wire i. through a self-induction coil m. One end of theother set of coils i is connected to the same wire through a deadresistance n. The opposite ends of these two circuits are con-nected to the contact m of a switch, the handle or lever of whichis in connection with the line-wire l', One end of the field cir-cuit of the synchronizing motor is connected to the wire l. Theother terminates in the switch-contact n. From the diagram itwill be readily seen that if the lever p be turned upon contact m,the torque motor will start by reason of the difference of phasebetween the currents in its two energizing circuits. Then whenthe desired speed is attained, if the lever p he shifted upon con-