POL TPIIASE CURRENTS.

r, 3

described already, but having on account of the polar projectionson the armature core, or other similar and well-known features,the properties of a synchronizing-motor, r. r.' represents theconductors of a line from an alternating current generator u.

Near the motor is placed a switch the action of which is thatof the one shown in the diagrams, which is constructed as fol-lows : f f' are two conducting plates or arms, pivoted at theirends and connected by an insulating cross-bar, h, so as to beshifted in parallelism. In the path of the bars f f' is the contact

2, which forms one terminal of the circuit through coils c, andthe contact I, which is one terminal of the circuit through coilsb. The opposite end of the wire of coils c is connected to thewire r. or bar f' , and the corresponding end of coils b is connectedto wire r/ and bar f; hence if the bars be shifted so as to bear oncontacts 2 and I both sets of coils n o will be included in the cir-cuit l i/ in multiple arc or derivation. In the path of the leversf f' are two other contact terminals, 1 and 3. The contact 1 isconnected to contact 2 through an artificial resistance, i, and con-tact 3 with contact I through a self-induction coil, j, so that whenthe switch levers are shifted upon the points 1 and 3 the circuitsof coils b and c will be connected in multiple arc or derivation tothe circuit l l', and will include the resistance and self-inductioncoil respectively. A third position of the switch is that in ■whichthe levers f and f' are shifted out of contact with both sets ofpoints. In this case the motor is entirely out of circuit.

The purpose and manner of operating the motor by these de-vices are as follows: The normal position of the switch, themotor being out of circuit, is off the contact points. Assumingthe generator to be running, and that it is desired to start themotor, the switch is shifted until its levers rest upon points 1 and

3. The two motor-circuits are thus connected with the generatorcircuit; but by reason of the presence of the resistance i in oneand the self-induction coil j in the other the coincidence of thephases of the current is disturbed sufficiently to produce a pro-gression of the poles, which starts the motor in rotation. Whenthe speed of the motor has run up to synchronism with thegenerator, or approximately so, the switch is shifted over uponthe points 2 and I, thus cutting out the coils i and .t, so that thecurrents in both circuits have the same phase; but the motornow runs as a synchronous motor.

It will be understood that when brought up to speed the mo