Functions of the commutator:
A commutator is a device, which under certain conditions changes ac into dc and vice versa.
The commutator is a form of rotating switch placed between the armature and external circuit and so arranged that it reverses the links to the external circuits at the instant of every reversal of the current in the armature coil. Thus it changes induced alternating currents in armature coils into direct currents in the external load circuits.