98

INVENTIONS OF NIKOLA TESLA.

tact n the entire current will pass through the held coils of thesynchronizing motor and the other will he doing no work.

The torque motor may be constructed and operated in variousways, many of which have already been touched upon. It is notnecessary that one motor be cut out of circuit while the other isin, for both may be acted upon by current at the same time, andMr. Tesla lias devised various dispositions or arrangements of thetwo motors for accomplishing this. Some of these arrangementsare illustrated in Figs. 81 to 85.

Referring to Fig. 81, let t designate the torque or multiplecircuit motor and s the synchronizing motor, n n' being the line-wires from a source of alternating current. The two circuits ofthe torque motor of different degrees of self-induction, and de-signated by n m, are connected in derivation to the wire l. Theyare then joined and connected to the energizing circuit of the

Fig. 80.

synchronizing motor, the opposite terminal of which is connectedto wire i/. The two motors are thus in series. To start themMr. Tesla short-circuits the synchronizing motor by a switch p',throwing the whole current through the torque motor. Thenwhen the desired speed is reached the switch i>' is opened, sothat the current passes through both motors. In such an arrange-ment as this it is obviously desirable for economical and otherreasons that a proper relation between the speeds of the twomotors should be observed.

In Fig. 82 another disposition is illustrated, s is the synchron-izing motor and t the torque motor, the circuits of both being inparallel, w is a circuit also in derivation to the motor circuitsand containing a switch v". s' is a switch in the synchronizingmotor circuit. On the start the switch s' is opened, cutting outthe motor s. Then v" is opened, throwing the entire current