POLYPHASE CURRENTS.

63

motor has a strong torque. When the desired speed is reached,the shunt around the armature-coils is opened and the currentdirected through both armature and field coils. Under theseconditions the motor has a strong tendency to synchronism.

In Fig. 49, a and b designate the field coils of the motor. Asthe circuits including these coils are of different self-induction,this is represented by a resistance coil r in circuit with a, and a

- Wffl- —dSTOSTOF—

Figs. 49, 50 and 51.

self-induction coil s in circuit with b. The same result may ofcourse be secured by the winding of the coils, o is the armaturecircuit, the terminals of which are rings a b. Brushes e d bearon these rings and connect with the line and field circuits. i> isthe shunt or short, circuit around the armature, e is the switchin the shunt.

It will be observed that in such a disposition as is illustrated in