Classification Of DC Motors

Excitation Method
The excitation method of a DC motor refers to how the excitation winding is powered to generate the magnetomotive force and establish the main magnetic field. Based on the different excitation methods, DC motors can be classified into the following types:

1. Separately Excited DC Motor
A separately excited DC motor is one where the excitation winding is not connected to the armature winding, but is powered by another DC power source. Permanent magnet DC motors can also be considered separately excited DC motors.

2. Shunt-Wound DC Motor
In a shunt-wound DC motor, the excitation winding is connected in parallel with the armature winding. As a shunt generator, the terminal voltage generated by the motor itself powers the excitation winding; as a shunt motor, the excitation winding and armature share the same power source, and in terms of performance, they are the same as separately excited DC motors.

3. Series-Wound DC Motor
In a series-wound DC motor, the excitation winding and armature winding are connected in series and then connected to a DC power source. The excitation current of this type of DC motor is the armature current.

4. Compound-wound DC motors have two excitation windings: a shunt winding and a series winding. If the magnetomotive force (MF) generated by the series winding is in the same direction as that generated by the shunt winding, it is called cumulative compound excitation. If the two MFs are in opposite directions, it is called differential compound excitation.

DC motors with different excitation methods have different characteristics. Generally, the main excitation methods for DC motors are shunt, series, and compound excitation, while the main excitation methods for DC generators are separately excited, shunt, and compound excitation.