DC Motor Performance

The performance of a DC motor is closely related to its excitation method. There are generally four types of excitation methods for DC motors: separately excited DC motors, DC shunt motors, DC series motors, and DC compound motors. Understanding the characteristics of each method is crucial:

1. Separately Excited DC Motor: The field winding is not electrically connected to the armature; the excitation circuit is supplied by a separate DC power source. Therefore, the excitation current is unaffected by the armature terminal voltage or armature current.

2. Shunt DC Motor: The circuit is parallel, resulting in current division. The voltage across the shunt winding is the same as the armature voltage. However, the field winding is made of thin wire with many turns, resulting in significant resistance and a smaller excitation current.

3. DC Series Motor: The current is connected in series, resulting in voltage division. The field winding is connected in series with the armature, so the magnetic field inside this type of motor changes significantly with changes in the armature current. To minimize losses and voltage drops in the excitation winding, its resistance should be as low as possible. Therefore, DC series motors are typically wound with thicker wires and have fewer turns.

4. DC compound motor: The magnetic flux of this motor is generated by the excitation current in both windings.