As the shaft rotates, the commutator reverses the flow of current in a winding. For a single armature winding, when the shaft has made one-half complete turn, the winding is now connected so that current flows through it in the opposite of the initial direction.

How does commutator reverse current?

The split ring commutator reverse the current in the armature every half revolution when the commutator changes contact from one brush to another. This reverse in current causes the forces acting on the coil to be reversed. This helps the coil continue to rotate in a clockwise direction.

How does commutator change direction?

In a generator the commutator picks off the current generated in the windings, reversing the direction of the current with each half turn, serving as a mechanical rectifier to convert the alternating current from the windings to unidirectional direct current in the external load circuit.