POLYPHASE OITRRENTS.

57

wires from a source of alternating currents n. Contact a is con-nected to brush « and coil b through a dead resistance u andwire v. Contact h is connected with brush f and coil a througha self-induction coil s and wire o. Contacts c and e are connectedto brushes o f, respectively, through the wires j> o, and contactd is directly connected with brush h. The lever/lias a widenedend, which may span the contacts a b. When in such positionand witli lever g on contact*#, the alternating currents divide be-tween the two motor-coils, and by reason of their different self-

l-

Fig. 41.

induction a difference of current-phase is obtained that starts themotor in rotation. In starting, the field-coils are short circuited.

When the motor has attained the desired speed, the switch isshifted to the position shown in dotted lines—that is to say, withthe levers/' g resting on points c e. This connects up the twoarmature coils in series, and the motor will then run as a syn-chronous motor. The field-coils are thrown into circuit with thedirect current source when the main switch is shifted.