A DC series motor is a type of DC motor that operates based on the principle of a series field winding. It is called a series motor because the field winding and armature winding are connected in series, resulting in the same current flowing through both windings.
The working principle of a DC series motor can be understood as follows:
- Stator: The stator of a DC series motor consists of two sets of windings: the armature winding and the series field winding. The armature winding is connected in series with the field winding.
- Armature: The armature is the rotating part of the motor, consisting of a coil of wire wound around a core. When a DC voltage is applied to the armature winding, a magnetic field is created.
- Series Field Winding: The series field winding is connected in series with the armature winding. It is made up of a few turns of thick wire wound around the pole pieces of the stator. The series field winding carries the same current as the armature winding.
- Magnetic Field Interaction: When a DC voltage is applied to the series field winding, it generates a magnetic field. This field interacts with the magnetic field produced by the armature current.
- Lorentz Force: According to Fleming’s left-hand rule, the interaction between the magnetic field and the armature current produces a force, known as the Lorentz force, that causes the armature to rotate.
- Speed and Torque Characteristics: The speed of a DC series motor is inversely proportional to the torque demand. As the load on the motor increases, the torque demand increases, leading to a decrease in speed. Conversely, when the load decreases, the speed increases.
DC series motors are known for their high starting torque, which makes them suitable for applications requiring a high starting torque, such as electric locomotives, cranes, and hoists. However, they have poor speed regulation, meaning their speed is highly dependent on the load. Additionally, without proper controls, DC series motors can become unstable or even self-destructive if operated at no load.