Rotor winding classification
There are three types of DC armature windings: stacked windings, wave windings and frog windings. The two outlet ends of each coil are connected to the two commutating segments of the commutator. The distance between the two on the circumferential surface of the commutator is called the commutator pitch, which is represented by Ys. Different types of windings have different commutator pitches.