The primary difference between lap winding and wave winding is the current (amperage) and voltage requirements of the generators. Generators requiring a high current with low voltage use lap winding. For a low current and high voltage, generators use wave winding. Both types of winding are required for direct current generators.
Another difference between lap and wave winding is the number of parallel paths. In lap winding, the number of parallel paths will always match the number of brushes and poles. On the other hand, with wave winding the number of paths is always two.
With lap winding, the finishing end of one coil connects to a commutator segment and to the starting end of the adjacent coil located under the same pole, continuing until all of the coils are connected. This type of winding receives its name from the fact that succeeding coils double or lap back. For this reason, lap winding may be referred to as multiple or parallel winding.
However, with wave winding, the two ends of each coil connect to commutator segments separated by the distance between the poles. This type of winding requires only one pair of brushes while allowing for the series addition of voltages in all the windings between the brushes. Series winding is another name for wave winding.