6(5

INVENTIONS OF NIKOLA TESLA.

lias the advantage that the closed armature-circuit imparts to themotor torque whet) the speed falls off, hut at the same time theconditions are such that the motor comes out of synchronismmore readily. To increase the tendency to synchronism, twocircuits may be used on the armature, one of which is short-cir-cuited on the start and both connected with the external circuitafter the synchronous speed is reached or passed. This disposi-tion is shown in Fig. 53. There are three contact-rings a i eand three brashes o d f, which connect the armature circuitswith the external circuit. On starting, the switch n is turned tocomplete the connection between one binding-post eand the field-coils. This short-circuits one of the armature-coils, as o. Theother coil f is out of circuit and open. When the motor is upto speed, the switch u is turned back, so that the connectionfrom binding-post p to the field coils is through the coil o, andswitch k is closed, thereby including coil f in multiple arc withthe field coils. Both armature coils aretlius active.

From the above-described instances it is evident that manyother dispositions for carrying out the invention are possible.