The DC motor is a rotating electric machine designed to operate from source of direct voltage. The basic type is a permanent magnet DC motor. The stator of a permanent magnet DC motor is composed of two or more permanent magnet pole pieces. The rotor is composed of windings that are connected to a mechanical commutator. The opposite polarities of the energized winding and the stator magnet attract and the rotor will rotate until it is aligned with the stator. Just as the rotor reaches alignment, the brushes move across the commutator contacts and energize the next winding.

Two other types of DC motors are series wound and shunt wound DC motors. These motors also use a similar rotor with brushes and a commutator. However, the stator uses windings instead of permanent magnets. The basic principle is still the same. A series wound DC motor has the stator windings in series with the rotor. A shunt wound DC motor has the stator windings in parallel with the rotor winding. A series wound motor is also called a universal motor. It is universal in the sense that it will run equally well using either an AC or a DC voltage source.