The DC motor is one of the oldest motors, and like any motor, DC motors consist of a stator and a rotor. The stator can be made of permanent magnets or poles that are bolted to the frame and extended at the end with pole extensions. A field winding is then wound around the poles and there may be auxiliary poles and auxiliary windings as well. The rotor is composed of sheets with grooves in which the working winding is placed. The sheets also have ventilation holes. Electric current to the rotor is supplied through brushes that rest on the commutator, which is mounted to the rotor.

The magnetic field excited by the field winding in the stator acts on the magnetic field generated in the rotor due to the current supplied to the field winding through the brushes and the commutator, resulting in a periodic change in the current flowing to the coil, also known as the armature. This, in turn, induces a rotational force, or torque, that constantly acts in the direction of rotation.

According to the way the field winding and armature are connected, DC motors can be divided into motors with external excitation or self-excitation. Motors with self-excitation are further classified into series, parallel (derivative) or series-parallel (compound) motors.