Commutator, Commutator segment

As shown in photo (a), a commutator consists of many copper commutator segments and insulated support. These are mainly used in DC motors, where they convert the DC current supplied from the brush while keeping in sliding contact with the brush from the mechanism as shown in photo (b). It is a mechanical device that converts the current from the power supply to rotating armature as alternating currents with proper timing and polarity. Fig. (c) shows the relationship between armature current, brushes, and field magnets and commutator which consists of eight segments,　while (d) is for a 18-segment motor.