What is the purpose of a commutator in a DC motor?

The purpose of a commutator in a DC motor is to reverse the polarity of the current flowing through the armature windings as the motor rotates. This action is essential because it ensures that the magnetic field generated by the armature windings consistently interacts with the fixed magnetic field (either permanent magnets or electromagnets) to produce continuous rotational motion.

As the armature spins, when it reaches the position where the magnetic forces would start to oppose each other, the commutator switches the direction of the current in the armature windings. This reversal allows the armature to maintain its rotational direction and keeps the motor running smoothly. Without the commutator's ability to reverse polarity, the motor would stall once the magnetic forces align in opposition.

This function of the commutator distinguishes it from other parts of the motor. While it assists in the power connection to the motor and influences the operational speed indirectly, its primary role is specifically in changing current direction within the armature to sustain motion.