With this simple machine the following principles can be demonstrated:
1. If the coil be rotated, alternating currents can be taken from the collector rings and it is called an alternator.
2. By connecting up the wires from the commutator segments, a direct current will flow in the external circuit making a dynamo.
3. Two separate currents can be taken from the armature, one supplying alternating current and the other direct current; such a machine is called a double current generator.
4. If a direct current be sent in the armature coil through the commutator, the coil will begin to rotate as in a motor and an alternating current can be taken out of the collector rings. Such an arrangement is called an inverted rotary converter.
5. If the machine be brought up to synchronous speed by external means and then supplied with alternating current at the collector rings, then if the direction of the current through the armature coil and the pole piece have the proper magnetic relation, the coil will continue to rotate in synchronism with the current. A direct current can be taken from the commutator, and when used thus, the machine is called simply a rotary converter.
Fig. 2,036.—Diagram of three phase rotary converter. In this type, the winding is tapped at three points 120° distant from each other, and leads connected with the corresponding commutator segments.